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:

int solution(vector<int> &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 C++

Time spent on task 17 minutes

Notes

not defined yet

Code: 08:10:00 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: 08:10:05 UTC, cpp, autosave

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// you can use includes, for example:
// #include <algorithm>

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
}

Code: 08:12:40 UTC, cpp, autosave

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1 2 3 4 5 6 7 8 9 10

// you can use includes, for example:
// #include <algorithm>

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    
}

Code: 08:13:10 UTC, cpp, autosave

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1 2 3 4 5 6 7 8 9 10 11

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    long sum = accumulate(A.begin(), A.end(), 0);
    return sum * 
}

Code: 08:13:21 UTC, cpp, autosave

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1 2 3 4 5 6 7 8 9 10 11

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    long sum = accumulate(A.begin(), A.end(), 0);
    return sum * (sum - 1)
}

Code: 08:23:38 UTC, cpp, autosave

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1 2 3 4 5 6 7 8 9 10

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    long sum = accumulate(A.begin(), A.end(), 0);
}

Code: 08:23:53 UTC, cpp, autosave

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    
}

Code: 08:24:23 UTC, cpp, autosave

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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix 
    }
}

Code: 08:24:53 UTC, cpp, autosave

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// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if 
    }
}

Code: 08:25:23 UTC, cpp, autosave

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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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
        }
    }
    return ans;
}

Code: 08:25:38 UTC, cpp, autosave

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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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > )
        }
    }
    return ans;
}

Code: 08:25:46 UTC, cpp, verify, result: Failed

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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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Analysis

Compile error

func.cpp: In function 'int solution(std::vector<int>&)':
func.cpp:10:5: error: expected ',' or ';' before 'vector'
     vector<int> prefixSum (m, 0);
     ^~~~~~
func.cpp:12:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < A.size(); i++) {
                     ~~^~~~~~~~~~
func.cpp:14:9: error: 'prefixSum' was not declared in this scope
         prefixSum[i] = prefix;
         ^~~~~~~~~
func.cpp:20:20: error: 'prefixSum' was not declared in this scope
             ans += prefixSum[m-1] - prefixSum[i];
                    ^~~~~~~~~

Code: 08:25:57 UTC, cpp, 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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
#include <vector>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size()
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Analysis

Compile error

func.cpp: In function 'int solution(std::vector<int>&)':
func.cpp:11:5: error: expected ',' or ';' before 'vector'
     vector<int> prefixSum (m, 0);
     ^~~~~~
func.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < A.size(); i++) {
                     ~~^~~~~~~~~~
func.cpp:15:9: error: 'prefixSum' was not declared in this scope
         prefixSum[i] = prefix;
         ^~~~~~~~~
func.cpp:21:20: error: 'prefixSum' was not declared in this scope
             ans += prefixSum[m-1] - prefixSum[i];
                    ^~~~~~~~~

Code: 08:26:09 UTC, cpp, 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 use includes, for example:
// #include <algorithm>
#include <numeric>
#include <vector>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size();
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Code: 08:26:11 UTC, cpp, 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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
#include <vector>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size();
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.001 s

Code: 08:26:17 UTC, cpp, 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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
#include <vector>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size();
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Analysis

expand all Example tests

▶

example
example test

✔

0.001 s

Code: 08:26:20 UTC, cpp, 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

// you can use includes, for example:
// #include <algorithm>
#include <numeric>
#include <vector>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    const int m = A.size();
    vector<int> prefixSum (m, 0);
    int prefix = 0;
    for (int i = 0; i < A.size(); i++) {
        prefix += A[i];
        prefixSum[i] = prefix;
    }
    
    int ans = 0;
    for (int i = m-1; i >= 0; i--) {
        if (A[i] == 0) {
            ans += prefixSum[m-1] - prefixSum[i];
            if (ans > 1000000000) return -1;
        }
    }
    return ans;
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example
example test

✔

0.001 s

expand all Correctness tests

▶

single
single element

✔

0.001 s

▶

double
two elements

✔

0.001 s

▶

simple
simple test

✔

0.001 s

▶

small_random
random, length = 100

✔

0.001 s

▶

small_random2
random, length = 1000

✔

0.001 s

expand all Performance tests

▶

medium_random
random, length = ~10,000

✔

0.001 s

▶

large_random
random, length = ~100,000

✔

0.004 s

▶

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

✔

0.004 s

▶

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

✔

0.004 s

▶

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

✔

0.004 s