Test results - Codility

Tasks Details

easy

1. TapeEquilibrium

Minimize the value |(A[0] + ... + A[P-1]) - (A[P] + ... + A[N-1])|.

Task Score

100%

Correctness

100%

Performance

100%

A non-empty array A consisting of N integers is given. Array A represents numbers on a tape.

Any integer P, such that 0 < P < N, splits this tape into two non-empty parts: A[0], A[1], ..., A[P − 1] and A[P], A[P + 1], ..., A[N − 1].

The difference between the two parts is the value of: |(A[0] + A[1] + ... + A[P − 1]) − (A[P] + A[P + 1] + ... + A[N − 1])|

In other words, it is the absolute difference between the sum of the first part and the sum of the second part.

For example, consider array A such that:

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

We can split this tape in four places:

P = 1, difference = |3 − 10| = 7

P = 2, difference = |4 − 9| = 5

P = 3, difference = |6 − 7| = 1

P = 4, difference = |10 − 3| = 7

Write a function:

function solution(A);

that, given a non-empty array A of N integers, returns the minimal difference that can be achieved.

For example, given:

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

the function should return 1, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [2..100,000];

each element of array A is an integer within the range [−1,000..1,000].

Solution

Programming language used JavaScript

Time spent on task 2 minutes

Notes

not defined yet

Task timeline

Code: 14:52:32 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: 14:52:39 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) {
    let leftNum = 0;
    let rightNum = A.reduce((a,b) => a+b);
    let answer = null;
    for (let i=0; i<A.length-1; i++) {
        leftNum += A[i];
        rightNum -= A[i];
        const diff = Math.abs(leftNum - rightNum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Code: 14:52:52 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) {
    let leftNum = 0;
    let rightNum = A.reduce((a,b) => a+b, 0);
    let answer = Number.MAX_;
    for (let i=0; i<A.length-1; i++) {
        leftNum += A[i];
        rightNum -= A[i];
        const diff = Math.abs(leftNum - rightNum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Code: 14:53:02 UTC, js, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

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

function solution(A) {
    let leftNum = 0;
    let rightNum = A.reduce((a,b) => a+b, 0);
    let answer = Number.MAX_SAFE_INTEGER;
    for (let i=0; i<A.length-1; i++) {
        leftNum += A[i];
        rightNum -= A[i];
        const diff = Math.abs(leftNum - rightNum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Code: 14:53:24 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) {
    let leftNum = 0;
    let rightNum = A.reduce((a,b) => a+b, 0);
    let answer = -1;
    for (let i=0; i<A.length-1; i++) {
        leftNum += A[i];
        rightNum -= A[i];
        const diff = Math.abs(leftNum - rightNum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Code: 14:53:40 UTC, js, autosave

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

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

function solution(A) {
    let leftSum = 0;
    let rightSum = A.reduce((a,b) => a+b, 0);
    let answer = -1;
    for (let i=0; i<A.length-1; i++) {
        leftSum += A[i];
        rightSum -= A[i];
        const diff = Math.abs(leftSum - rightSum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Code: 14:53:45 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) {
    let leftSum = 0;
    let rightSum = A.reduce((a,b) => a+b, 0);
    let answer = -1;
    for (let i=0; i<A.length-1; i++) {
        leftSum += A[i];
        rightSum -= A[i];
        const diff = Math.abs(leftSum - rightSum)
        if (answer > diff) {
            answer = diff
        }
    }
    return answer
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got -1 expected 1

0.072 s

WRONG ANSWER, got -1 expected 1

Code: 14:54:03 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) {
    let leftSum = 0;
    let rightSum = A.reduce((a,b) => a+b, 0);
    let answer = null;
    for (let i=0; i<A.length-1; i++) {
        leftSum += A[i];
        rightSum -= A[i];
        const diff = Math.abs(leftSum - rightSum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Analysis

expand all Example tests

▶

example
example test

✔

0.072 s

Code: 14:54:10 UTC, js, 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

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

function solution(A) {
    let leftSum = 0;
    let rightSum = A.reduce((a,b) => a+b, 0);
    let answer = null;
    for (let i=0; i<A.length-1; i++) {
        leftSum += A[i];
        rightSum -= A[i];
        const diff = Math.abs(leftSum - rightSum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Analysis

expand all Example tests

▶

example
example test

✔

0.072 s

Code: 14:54:12 UTC, js, 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

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

function solution(A) {
    let leftSum = 0;
    let rightSum = A.reduce((a,b) => a+b, 0);
    let answer = null;
    for (let i=0; i<A.length-1; i++) {
        leftSum += A[i];
        rightSum -= A[i];
        const diff = Math.abs(leftSum - rightSum)
        if (answer === null || answer > diff) {
            answer = diff
        }
    }
    return answer
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example
example test

✔

0.068 s

expand all Correctness tests

▶

double
two elements

✔

0.072 s

0.068 s

0.072 s

▶

simple_positive
simple test with positive numbers, length = 5

✔

0.068 s

▶

simple_negative
simple test with negative numbers, length = 5

✔

0.068 s

▶

simple_boundary
only one element on one of the sides

✔

0.068 s

▶

small_random
random small, length = 100

✔

0.068 s

▶

small_range
range sequence, length = ~1,000

✔

0.072 s

▶

small
small elements

✔

0.072 s

expand all Performance tests

▶

medium_random1
random medium, numbers from 0 to 100, length = ~10,000

✔

0.084 s

▶

medium_random2
random medium, numbers from -1,000 to 50, length = ~10,000

✔

0.080 s

▶

large_ones
large sequence, numbers from -1 to 1, length = ~100,000

✔

0.104 s

▶

large_random
random large, length = ~100,000

✔

0.112 s

▶

large_sequence
large sequence, length = ~100,000

✔

0.096 s

▶

large_extreme
large test with maximal and minimal values, length = ~100,000

✔

0.112 s

0.108 s