Test results - Codility

Tasks Details

medium

1. NumberOfDiscIntersections

Compute the number of intersections in a sequence of discs.

Task Score

100%

Correctness

100%

Performance

100%

We draw N discs on a plane. The discs are numbered from 0 to N − 1. An array A of N non-negative integers, specifying the radiuses of the discs, is given. The J-th disc is drawn with its center at (J, 0) and radius A[J].

We say that the J-th disc and K-th disc intersect if J ≠ K and the J-th and K-th discs have at least one common point (assuming that the discs contain their borders).

The figure below shows discs drawn for N = 6 and A as follows:

A[0] = 1 A[1] = 5 A[2] = 2 A[3] = 1 A[4] = 4 A[5] = 0

There are eleven (unordered) pairs of discs that intersect, namely:

discs 1 and 4 intersect, and both intersect with all the other discs;

disc 2 also intersects with discs 0 and 3.

Write a function:

class Solution { public int solution(int[] A); }

that, given an array A describing N discs as explained above, returns the number of (unordered) pairs of intersecting discs. The function should return −1 if the number of intersecting pairs exceeds 10,000,000.

Given array A shown above, the function should return 11, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000];

each element of array A is an integer within the range [0..2,147,483,647].

Solution

Programming language used Java 8

Time spent on task 9 minutes

Notes

not defined yet

Task timeline

Code: 03:38:01 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        // write your code in Java SE 8
    }
}

Code: 03:39:06 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int re
    }
}

Code: 03:39:17 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;

        return result;
    }
}

Code: 03:39:48 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;

        
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:39:59 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;
        

        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:40:29 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;

        long[] left = new long[A.length];
        

        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:40:59 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        for (int idx = 0; idx < A.length; idx++) {
                
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:41:20 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:41:48 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left point and right point.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:41:58 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:42:16 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:42:37 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:43:00 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        for (int idx = 0; idx < A.length; idx++) {
            
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:43:22 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right)
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:43:43 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:44:14 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Caclu
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:44:24 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Caculate
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:44:35 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:44:46 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate 
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:44:59 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:45:29 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        // If the number of intersecting pairs
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:45:39 UTC, java, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        // If the number of intersecting pairs excceds 10,000,000.
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Code: 03:45:46 UTC, java, verify, result: Passed

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        // If the number of intersecting pairs excceds 10,000,000.
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.004 s

Code: 03:46:11 UTC, java, verify, result: Passed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        // If the number of intersecting pairs excceds 10,000,000.
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.004 s

Code: 03:46:16 UTC, java, final, score: 100

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

import java.util.Arrays;

class Solution {
    public int solution(int[] A) {
        int result = 0;
        long[] left = new long[A.length];
        long[] right = new long[A.length];
        // Save left and right point each array.
        for (int idx = 0; idx < A.length; idx++) {
            left[idx] = idx - (long) A[idx];
            right[idx] = idx + (long) A[idx];
        }
        Arrays.sort(left);
        Arrays.sort(right);
        int num = 0;
        // Calculate intersects with left and right point.
        for (int idx = 0; idx < A.length; idx++) {
            while (num < A.length && right[idx] >= left[num]) {
                result += num;
                result -= idx;
                num++;
            }
        }
        // If the number of intersecting pairs excceds 10,000,000.
        if (result > 10000000) {
            return -1;
        }
        return result;
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N*log(N)) or O(N)

expand all Example tests

▶

example1
example test

✔

0.004 s

expand all Correctness tests

▶

simple1

✔

0.008 s

▶

simple2

✔

0.008 s

▶

simple3

✔

0.008 s

▶

extreme_small
empty and [10]

✔

0.004 s

▶

small1

✔

0.004 s

▶

small2

✔

0.004 s

▶

small3

✔

0.008 s

▶

overflow
arithmetic overflow tests

✔

0.004 s

expand all Performance tests

▶

medium1

✔

0.008 s

▶

medium2

✔

0.012 s

▶

medium3

✔

0.020 s

▶

medium4

✔

0.032 s

▶

10M_intersections
10.000.000 intersections

✔

0.028 s

▶

big1

✔

0.144 s

0.004 s

▶

big2

✔

0.292 s

0.004 s

▶

big3
[0]*100.000

✔

0.164 s

0.008 s