Test results - Codility

Tasks Details

easy

1. PassingCars

Count the number of passing cars on the road.

Task Score

100%

Correctness

100%

Performance

100%

A non-empty array A consisting of N integers is given. The consecutive elements of array A represent consecutive cars on a road.

Array A contains only 0s and/or 1s:

0 represents a car traveling east,

1 represents a car traveling west.

The goal is to count passing cars. We say that a pair of cars (P, Q), where 0 ≤ P < Q < N, is passing when P is traveling to the east and Q is traveling to the west.

For example, consider array A such that:

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

We have five pairs of passing cars: (0, 1), (0, 3), (0, 4), (2, 3), (2, 4).

Write a function:

function solution(A);

that, given a non-empty array A of N integers, returns the number of pairs of passing cars.

The function should return −1 if the number of pairs of passing cars exceeds 1,000,000,000.

For example, given:

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

the function should return 5, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..100,000];

each element of array A is an integer that can have one of the following values: 0, 1.

Solution

Programming language used JavaScript

Time spent on task 8 minutes

Notes

not defined yet

Code: 07:29:16 UTC, java, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11

// 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: 07:29:21 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6

// 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: 07:32:50 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6

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

function solution(A) {
    
}

Code: 07:33:21 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11

// 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 zeros = [];
    const ones = [];

    for (let i = 0; i < )
}

Code: 07:33:31 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13

// 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 zeros = [];
    const ones = [];

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

Code: 07:34:02 UTC, js, autosave

show code in pop-up

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

// 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 zeros = [0];
    const ones = [0];

    for (let i = 0; i < N; i++) {
        zeros.push(zeros[i]);
        ones.push(ones[i]);

        if (A[i] =)
    }
}

Code: 07:34:33 UTC, js, autosave

show code in pop-up

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

// 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 zeros = [0];
    const ones = [0];

    for (let i = 0; i < N; i++) {
        zeros.push(zeros[i]);
        ones.push(ones[i]);

        if (A[i] === 0) {
            zeros[i + 1]++;
        } else {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

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

Code: 07:34:44 UTC, js, autosave

show code in pop-up

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

// 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 zeros = [0];
    const ones = [0];

    for (let i = 0; i < N; i++) {
        zeros.push(zeros[i]);
        ones.push(ones[i]);

        if (A[i] === 0) {
            zeros[i + 1]++;
        } else {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

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

Code: 07:35:01 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

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

Code: 07:35:25 UTC, js, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

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

Code: 07:35:44 UTC, js, verify, result: Failed

show code in pop-up

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

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            count += ones[N] - ones[i + 1];
            
            if (count > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

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:

ReferenceError: count is not defined
    at solution (solution.js:20:13)
    at solutionWrapper (/tmp/exec.js:402:28)
    at Promise.resolve.then (/tmp/exec.js:428:24)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
    at Function.Module.runMain (module.js:686:11)
    at startup (bootstrap_node.js:187:16)
    at bootstrap_node.js:608:3

Code: 07:35:55 UTC, js, verify, result: Failed

show code in pop-up

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

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    const passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            passingCount += ones[N] - ones[i + 1];
            
            if (passingCount > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

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:

TypeError: Assignment to constant variable.
    at solution (solution.js:20:26)
    at solutionWrapper (/tmp/exec.js:402:28)
    at Promise.resolve.then (/tmp/exec.js:428:24)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
    at Function.Module.runMain (module.js:686:11)
    at startup (bootstrap_node.js:187:16)
    at bootstrap_node.js:608:3

Code: 07:36:01 UTC, js, autosave

show code in pop-up

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

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    let passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            passingCount += ones[N] - ones[i + 1];
            
            if (passingCount > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

Code: 07:36:02 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 18 19 20 21 22 23 24 25 26 27 28 29

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    let passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            passingCount += ones[N] - ones[i + 1];
            
            if (passingCount > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.068 s

Code: 07:36:16 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 18 19 20 21 22 23 24 25 26 27 28 29

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    let passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            passingCount += ones[N] - ones[i + 1];
            
            if (passingCount > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.068 s

Code: 07:36:18 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 18 19 20 21 22 23 24 25 26 27 28 29

// 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 ones = [0];

    for (let i = 0; i < N; i++) {
        ones.push(ones[i]);

        if (A[i] === 1) {
            ones[i + 1]++;
        }
    }

    let passingCount = 0;

    for (let i = 0; i < N; i++) {
        if (A[i] === 0) {
            passingCount += ones[N] - ones[i + 1];
            
            if (passingCount > 1000000000) {
                return -1
            }
        }
    }

    return passingCount;
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example
example test

✔

0.076 s

expand all Correctness tests

▶

single
single element

✔

0.076 s

0.072 s

▶

double
two elements

✔

0.072 s

0.076 s

▶

simple
simple test

✔

0.076 s

▶

small_random
random, length = 100

✔

0.076 s

▶

small_random2
random, length = 1000

✔

0.076 s

expand all Performance tests

▶

medium_random
random, length = ~10,000

✔

0.088 s

▶

large_random
random, length = ~100,000

✔

0.108 s

▶

large_big_answer
0..01..1, length = ~100,000

✔

0.108 s

0.100 s

▶

large_alternate
0101..01, length = ~100,000

✔

0.104 s

▶

large_extreme
large test with all 1s/0s, length = ~100,000

✔

0.108 s

0.104 s