Test results - Codility

Tasks Details

medium

1. ArrayInversionCount

Compute number of inversion in an array.

Task Score

100%

Correctness

100%

Performance

100%

An array A consisting of N integers is given. An inversion is a pair of indexes (P, Q) such that P < Q and A[Q] < A[P].

Write a function:

function solution(A);

that computes the number of inversions in A, or returns −1 if it exceeds 1,000,000,000.

For example, in the following array:

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

there are four inversions:

(1,2) (1,3) (1,5) (4,5)

so the function should return 4.

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 JavaScript

Time spent on task 2 minutes

Notes

not defined yet

Code: 14:11:05 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");

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

Code: 14:11:08 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
}

Code: 14:11:15 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Code: 14:11:37 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Code: 14:11:40 UTC, js, verify, result: Passed

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.072 s

Code: 14:12:04 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Code: 14:12:18 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Code: 14:12:33 UTC, js, verify, result: Passed

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

User test case 1:

[]

User test case 2:

[1, 2, 3, 4, 5, 6]

User test case 3:

[6, 5, 4, 3, 2, 1]

User test case 4:

[-2147483648, 0, 2147483647]

Analysis

expand all Example tests

▶

example1
example test

✔

0.068 s

expand all User tests

▶

test_data1

✔

0.068 s

OK
function result: 0

▶

test_data2

✔

0.068 s

OK
function result: 0

▶

test_data3

✔

0.068 s

OK
function result: 15

▶

test_data4

✔

0.068 s

OK
function result: 0

Code: 14:12:46 UTC, js, autosave

show code in pop-up

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Code: 14:12:54 UTC, js, verify, result: Passed

show code in pop-up

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

User test case 1:

[]

User test case 2:

[1, 2, 3, 4, 5, 6]

User test case 3:

[6, 5, 4, 3, 2, 1]

User test case 4:

[-2147483648, 0, 2147483647]

User test case 5:

[2147483647, 0, -2147483648]

Analysis

expand all Example tests

▶

example1
example test

✔

0.072 s

expand all User tests

▶

test_data1

✔

0.072 s

OK
function result: 0

▶

test_data2

✔

0.072 s

OK
function result: 0

▶

test_data3

✔

0.072 s

OK
function result: 15

▶

test_data4

✔

0.072 s

OK
function result: 0

▶

test_data5

✔

0.072 s

OK
function result: 3

Code: 14:12:59 UTC, js, verify, result: Passed

show code in pop-up

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

User test case 1:

[]

User test case 2:

[1, 2, 3, 4, 5, 6]

User test case 3:

[6, 5, 4, 3, 2, 1]

User test case 4:

[-2147483648, 0, 2147483647]

User test case 5:

[2147483647, 0, -2147483648]

Analysis

expand all Example tests

▶

example1
example test

✔

0.068 s

expand all User tests

▶

test_data1

✔

0.068 s

OK
function result: 0

▶

test_data2

✔

0.068 s

OK
function result: 0

▶

test_data3

✔

0.068 s

OK
function result: 15

▶

test_data4

✔

0.072 s

OK
function result: 0

▶

test_data5

✔

0.072 s

OK
function result: 3

Code: 14:13:02 UTC, js, final, score: 100

show code in pop-up

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    return mergeSortAndCount(A, 0, A.length - 1)
}

function mergeSortAndCount(A, start, end) {
    let count = 0;
    
    if (start < end) {
        let mid = parseInt((start + end) / 2);
        count += mergeSortAndCount(A, start, mid);
        count += mergeSortAndCount(A, mid + 1, end);
        count += mergeAndCount(A, start, mid, end);
        if (count > 1000000000) {
            return -1;
        }
    }
    return count;
}

function mergeAndCount(A, start, mid, end) {
    let left = A.slice(start, mid + 1);
    let right = A.slice(mid + 1, end + 1);
    
    let i = 0;
    let j = 0;
    let k = start;
    let swaps = 0;
    while (i < left.length && j < right.length) {
        if (left[i] <= right[j]) {
            A[k++] = left[i++];
        } else {
            A[k++] = right[j++];
            swaps += (mid + 1) - (start + i)
        }
    }
    while (i < left.length) {
        A[k++] = left[i++];
    }
    while (j < right.length) {
        A[k++] = right[j++]
    }
    
    return swaps;
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N*log(N))

expand all Example tests

▶

example1
example test

✔

0.068 s

expand all Correctness tests

▶

simple1

✔

0.068 s

▶

simple2

✔

0.072 s

▶

simple3

✔

0.068 s

▶

extreme_0_inv
[0], [], [1,2,3], [1,1,1]

✔

0.068 s

▶

medium1
n=100

✔

0.072 s

▶

medium2
n=200

✔

0.068 s

expand all Performance tests

▶

medium3
n=1000

✔

0.080 s

▶

big1
n=10000

✔

0.100 s

▶

big2
n=20000

✔

0.112 s

▶

big3
n=30000

✔

0.120 s

▶

big_monotonic
long descending and non-ascending sequence

✔

0.128 s