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

function solution(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 JavaScript

Time spent on task 7 minutes

Notes

not defined yet

Code: 09:55:37 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");

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

Code: 09:56:10 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if ()
    }
}

Code: 09:56:20 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        
    }
}

Code: 09:59:13 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (sta)
    }
}

Code: 09:59:31 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack) {
            stack.push(A[i]);
        }
    }
}

Code: 09:59:43 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        }

        
    }
}

Code: 09:59:59 UTC, js, verify, result: Failed

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

function solution(A) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }

        console.log(stack);
    }
}

Analysis

expand all Example tests

▶

example
example test

✘

RUNTIME ERROR
tested program terminated with exit code 1

0.072 s

RUNTIME ERROR, tested program terminated with exit code 1

stderr:

Invalid result type, integer expected, 'undefined' found
Perhaps you are missing a 'return'?

stdout:

[ 3 ]
[]
[ 3 ]
[]
[ 3 ]
[]
[ 3 ]
[ 3, 3 ]

Code: 10:00:11 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }

    
}

Code: 10:00:21 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }

    if ()
}

Code: 10:00:52 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    

    let count = 0;
    for (let i = 0; i < N; i++) {
        if (A[i] === )
    }
}

Code: 10:01:23 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
    const candidate = stack.pop();

    let count = 0;
    for (let i = 0; i < N; i++) {
        if (A[i] === )
    }
    }
    
    return -1;
}

Code: 10:01:43 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
        const candidate = stack.pop();
        const 

        let count = 0;
        for (let i = 0; i < N; i++) {
            if (A[i] === candidate) {
                count++;

                if (count >= Math.floor())
            }
        }
    }
    
    return -1;
}

Code: 10:02:14 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
        const candidate = stack.pop();
        const minCount = Math.floor(N / 2) + 1;

        let count = 0;
        for (let i = 0; i < N; i++) {
            if (A[i] === candidate) {
                count++;

                if (count >= minCount)
            }
        }
    }
    
    return -1;
}

Code: 10:02:18 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
        const candidate = stack.pop();
        const minCount = Math.floor(N / 2) + 1;

        let count = 0;
        for (let i = 0; i < N; i++) {
            if (A[i] === candidate) {
                count++;

                if (count >= minCount) {
                    return i;
                }
            }
        }
    }
    
    return -1;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.104 s

Code: 10:02:26 UTC, js, 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

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

function solution(A) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
        const candidate = stack.pop();
        const minCount = Math.floor(N / 2) + 1;

        let count = 0;
        for (let i = 0; i < N; i++) {
            if (A[i] === candidate) {
                count++;

                if (count >= minCount) {
                    return i;
                }
            }
        }
    }
    
    return -1;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.068 s

Code: 10:02:29 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) {
    const N = A.length;
    const stack = [];

    for (let i = 0; i < N; i++) {
        if (stack.length === 0 || stack[stack.length - 1] === A[i]) {
            stack.push(A[i]);
        } else {
            stack.pop();
        }
    }
    if (stack.length > 0) {
        const candidate = stack.pop();
        const minCount = Math.floor(N / 2) + 1;

        let count = 0;
        for (let i = 0; i < N; i++) {
            if (A[i] === candidate) {
                count++;

                if (count >= minCount) {
                    return i;
                }
            }
        }
    }
    
    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

✔

0.068 s

expand all Correctness tests

▶

small_nondominator
all different and all the same elements

✔

0.068 s

▶

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

✔

0.072 s

▶

small
small test

✔

0.068 s

▶

small_pyramid
decreasing and plateau, small

✔

0.068 s

▶

extreme_empty_and_single_item
empty and single element arrays

✔

0.068 s

▶

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

✔

0.068 s

▶

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

✔

0.068 s

▶

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

✔

0.068 s

expand all Performance tests

▶

medium_pyramid
decreasing and plateau, medium

✔

0.084 s

▶

large_pyramid
decreasing and plateau, large

✔

0.112 s

▶

medium_random
random test with dominator, N = 10,000

✔

0.084 s

▶

large_random
random test with dominator, N = 100,000

✔

0.112 s