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

Task timeline

Code: 13:54:53 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: 13:54:56 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: 13:55:02 UTC, js, autosave

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var total = 0;
function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    mergeSort(A);
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Code: 13:55:16 UTC, js, autosave

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var total = 0;
const LIMIT = 
function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    mergeSort(A);
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Code: 13:55:30 UTC, js, autosave

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var total = 0;
const LIMIT = 1000000000;

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

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Code: 13:55:44 UTC, js, autosave

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var total = 0;
const LIMIT = 1000000000;

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

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
            
            if (total >)
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Code: 13:56:14 UTC, js, autosave

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var total = 0;
const LIMIT = 1000000000;

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    try {
        mergeSort(A);
    } catc
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
            
            if (total > LIMIT) {
                throw new Error('Limit exceeded');
            }
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Code: 13:56:22 UTC, js, verify, result: Passed

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var total = 0;
const LIMIT = 1000000000;

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    try {
        mergeSort(A);
    } catch (e) {
        return -1;
    }
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
            
            if (total > LIMIT) {
                throw new Error('Limit exceeded');
            }
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.072 s

Code: 13:56:27 UTC, js, verify, result: Passed

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var total = 0;
const LIMIT = 1000000000;

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    try {
        mergeSort(A);
    } catch (e) {
        return -1;
    }
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
            
            if (total > LIMIT) {
                throw new Error('Limit exceeded');
            }
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.072 s

Code: 13:56:29 UTC, js, final, score: 100

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var total = 0;
const LIMIT = 1000000000;

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    try {
        mergeSort(A);
    } catch (e) {
        return -1;
    }
    
    return total;
}

function mergeSort(unsortedArray) {
    if (unsortedArray.length <= 1) {
        return unsortedArray;
    }   
    
    const mid = parseInt(unsortedArray.length / 2);
    const left = unsortedArray.slice(0, mid);
    const right = unsortedArray.slice(mid);
    
    return merge(
        mergeSort(left),
        mergeSort(right),
    );;
}

function merge(left, right) {
    const res = [];
    let rightIndex = 0, leftIndex = 0;
    let indif = 0;
    
    while (rightIndex < right.length && leftIndex < left.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            res.push(left[leftIndex]);
            leftIndex++
        } else {
            res.push(right[rightIndex]);
            rightIndex++;
            
            const restInLeft = left.length - leftIndex;
            total += restInLeft;
            
            if (total > LIMIT) {
                throw new Error('Limit exceeded');
            }
        }
    }
    
    return [...res, ...left.slice(leftIndex), ...right.slice(rightIndex)]
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N*log(N))

expand all Example tests

▶

example1
example test

✔

0.072 s

expand all Correctness tests

▶

simple1

✔

0.068 s

▶

simple2

✔

0.068 s

▶

simple3

✔

0.072 s

▶

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

✔

0.068 s

0.080 s

0.068 s

▶

medium1
n=100

✔

0.072 s

▶

medium2
n=200

✔

0.072 s

expand all Performance tests

▶

medium3
n=1000

✔

0.088 s

▶

big1
n=10000

✔

0.124 s

▶

big2
n=20000

✔

0.156 s

▶

big3
n=30000

✔

0.172 s

▶

big_monotonic
long descending and non-ascending sequence

✔

0.204 s

0.200 s