Test results - Codility

Tasks Details

easy

1. Dominator

Find an index of an array such that its value occurs at more than half of indices in the array.

Task Score

100%

Correctness

100%

Performance

100%

An array A consisting of N integers is given. The dominator of array A is the value that occurs in more than half of the elements of A.

For example, consider array A such that

A[0] = 3 A[1] = 4 A[2] = 3 A[3] = 2 A[4] = 3 A[5] = -1 A[6] = 3 A[7] = 3

The dominator of A is 3 because it occurs in 5 out of 8 elements of A (namely in those with indices 0, 2, 4, 6 and 7) and 5 is more than a half of 8.

Write a function

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

that, given an array A consisting of N integers, returns index of any element of array A in which the dominator of A occurs. The function should return −1 if array A does not have a dominator.

For example, given array A such that

A[0] = 3 A[1] = 4 A[2] = 3 A[3] = 2 A[4] = 3 A[5] = -1 A[6] = 3 A[7] = 3

the function may return 0, 2, 4, 6 or 7, 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 [−2,147,483,648..2,147,483,647].

Solution

Programming language used Java 8

Time spent on task 8 minutes

Notes

not defined yet

Task timeline

Code: 05:56:59 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) {
        // write your code in Java SE 8
    }
}

Code: 05:58:39 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) {
        Map
    }
}

Code: 05:59:09 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int num : A) {
            map.put(n)
        }
    }
}

Code: 05:59:24 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
    }
}

Code: 05:59:34 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // 
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
    }
}

Code: 06:00:05 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Ca
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
    }
}

Code: 06:00:20 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");

import java.util.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
    }
}

Code: 06:00:51 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry)
        }
    }
}

Code: 06:01:10 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
    }
}

Code: 06:01:35 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not h
        if (max <= A.length / 2) {
            return -1;
        }
    }
}

Code: 06:01:49 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size.
        if (max <= A.length / 2) {
            return -1;
        }
    }
}

Code: 06:02:06 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");

import java.util.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
    }
}

Code: 06:02:36 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key)
        }
    }
}

Code: 06:02:47 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Code: 06:02:47 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Analysis

expand all Example tests

▶

example
example test

✔

0.008 s

Code: 06:02:57 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 37

// 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find any
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Code: 06:03:07 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int key = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                key = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find any index of key.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Code: 06:03:19 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find any index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Code: 06:03:26 UTC, java, verify, result: Failed

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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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find any index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == key) {
                return idx;
            }
        }
        return -1;
    }
}

Analysis

Compile error

Solution.java:31: error: cannot find symbol
            if (A[idx] == key) {
                          ^
  symbol:   variable key
  location: class Solution
1 error

Code: 06:03:34 UTC, java, verify, result: Passed

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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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find any index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == num) {
                return idx;
            }
        }
        return -1;
    }
}

Analysis

expand all Example tests

▶

example
example test

✔

0.008 s

Code: 06:03:58 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 37

// 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == num) {
                return idx;
            }
        }
        return -1;
    }
}

Code: 06:04:04 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 37

// 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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == num) {
                return idx;
            }
        }
        return -1;
    }
}

Analysis

expand all Example tests

▶

example
example test

✔

0.012 s

Code: 06:04:09 UTC, java, final, score: 100

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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.Map;
import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        // Calcualte how many numbers are in the array(A).
        for (int num : A) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int num = 0;
        int max = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() > max) {
                num = entry.getKey();
                max = entry.getValue();
            }
        }
        // If not half of array(A)'s size, return -1.
        if (max <= A.length / 2) {
            return -1;
        }
        // Find index of num.
        for (int idx = 0; idx < A.length; idx++) {
            if (A[idx] == num) {
                return idx;
            }
        }
        return -1;
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

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

expand all Example tests

▶

example
example test

✔

0.008 s

expand all Correctness tests

▶

small_nondominator
all different and all the same elements

✔

0.012 s

▶

small_half_positions
half elements the same, and half + 1 elements the same

✔

0.012 s

▶

small
small test

✔

0.012 s

▶

small_pyramid
decreasing and plateau, small

✔

0.012 s

▶

extreme_empty_and_single_item
empty and single element arrays

✔

0.012 s

0.008 s

▶

extreme_half1
array with exactly N/2 values 1, N even + [0,0,1,1,1]

✔

0.012 s

▶

extreme_half2
array with exactly floor(N/2) values 1, N odd + [0,0,1,1,1]

✔

0.008 s

▶

extreme_half3
array with exactly ceil(N/2) values 1 + [0,0,1,1,1]

✔

0.012 s

expand all Performance tests

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medium_pyramid
decreasing and plateau, medium

✔

0.056 s

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large_pyramid
decreasing and plateau, large

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0.524 s

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medium_random
random test with dominator, N = 10,000

✔

0.064 s

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large_random
random test with dominator, N = 100,000

✔

0.568 s