Test results - Codility

Tasks Details

medium

1. MissingInteger

Find the smallest positive integer that does not occur in a given sequence.

66%

80%

50%

This is a demo task.

Write a function:

int solution(vector<int> &A);

that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.

For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.

Given A = [1, 2, 3], the function should return 4.

Given A = [−1, −3], the function should return 1.

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 within the range [−1,000,000..1,000,000].

Solution

Programming language used C++

Time spent on task 4 minutes

Notes

not defined yet

Task timeline

Code: 10:01:12 UTC, cpp, verify, result: Passed

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 33 34 35 36 37 38

// 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;

#include <algorithm>

int solution(vector<int> &A) {
    // write your code in C++11
    std::sort ( A.begin(), A.end());
    
    int result = 0;
    
    if ( *(A.begin()) > 1 )
        result = 1;
    else
    {
        int beforeValue = 0;
        for ( vector<int>::iterator it = A.begin(); it < A.end(); it++ )
        {
            if ( *it <= 0 )
                continue; 
            if ( *it > beforeValue+1 )
            {
                result = beforeValue+1;
                break;
            }
            beforeValue = *it;
        }
        if ( beforeValue == 0 )
            result = 1;
        else if ( beforeValue == *(A.end()) )
            result = *(A.end()) + 1;
    }
    
    return result;
}

Analysis

▶

example
example (without minus)

✔

Code: 10:01:21 UTC, cpp, verify, result: Passed

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 33 34 35 36 37 38

// 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;

#include <algorithm>

int solution(vector<int> &A) {
    // write your code in C++11
    std::sort ( A.begin(), A.end());
    
    int result = 0;
    
    if ( *(A.begin()) > 1 )
        result = 1;
    else
    {
        int beforeValue = 0;
        for ( vector<int>::iterator it = A.begin(); it < A.end(); it++ )
        {
            if ( *it <= 0 )
                continue; 
            if ( *it > beforeValue+1 )
            {
                result = beforeValue+1;
                break;
            }
            beforeValue = *it;
        }
        if ( beforeValue == 0 )
            result = 1;
        else if ( beforeValue == *(A.end()) )
            result = *(A.end()) + 1;
    }
    
    return result;
}

Analysis

▶

example
example (without minus)

✔

Code: 10:01:26 UTC, cpp, final, score: 66

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 33 34 35 36 37 38

// 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;

#include <algorithm>

int solution(vector<int> &A) {
    // write your code in C++11
    std::sort ( A.begin(), A.end());
    
    int result = 0;
    
    if ( *(A.begin()) > 1 )
        result = 1;
    else
    {
        int beforeValue = 0;
        for ( vector<int>::iterator it = A.begin(); it < A.end(); it++ )
        {
            if ( *it <= 0 )
                continue; 
            if ( *it > beforeValue+1 )
            {
                result = beforeValue+1;
                break;
            }
            beforeValue = *it;
        }
        if ( beforeValue == 0 )
            result = 1;
        else if ( beforeValue == *(A.end()) )
            result = *(A.end()) + 1;
    }
    
    return result;
}

Analysis summary

The following issues have been detected: wrong answers.

Analysis

▶

example
example (without minus)

✔

▶

extreme_single
a single element

✘

WRONG ANSWER
got 0 expected 2

▶

simple
simple test

✔

▶

extreme_min_max_int
MININT and MAXINT (with minus)

✔

▶

positive_only
shuffled sequence of 0...100 and then 102...200

✔

▶

negative_only
shuffled sequence -100 ... -1

✔

▶

medium
chaotic sequences length=10005 (with minus)

✘

WRONG ANSWER
got 0 expected 101

▶

large_1
chaotic + sequence 1, 2, ..., 40000 (without minus)

✔

▶

large_2
shuffled sequence 1, 2, ..., 100000 (without minus)

✘

WRONG ANSWER
got 0 expected 100001

▶

large_3
chaotic + many -1, 1, 2, 3 (with minus)

✔