CODEWITHSUNDEEP
c++stdvector
luke97
luke97

Reputation: 1

Getting vector subscript out of range exception

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector <int> arr = { -12, 14, 71, 123, 12, -14, 5, 5, -75, 12, -1, 51, 12, 61, -61, -13 };
    int n = arr.size();
    for (int i = 0; i < n; i++)
    {
        for (int j=0;j<n;j++)
        {
            if (arr[j] < arr[j + 1])
            {
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
            else if (arr[j] == arr[j + 1])
            {
                for (int a = j + 1; a < n; a++)
                {
                    arr[a] = arr[a + 1];
                }
            }
        }
    }
    for (int i : arr)
    {
        cout << i << endl;
    }
    return 0;
}

It works if I use an array but it shown "vector subscript out of range" when I use vector. Could anyone please explain why is it an error there?

Upvotes: 0

Views: 147

Answers (3)

ashchk
ashchk

Reputation: 191

your vector element size is n. But,you are using index over n incase of arr[j+1] and arr[a+1].

Just put condition checking, i < n-1 , j < n-1 and a < n-1

Here is the updated code:

vector <int> arr = { -12, 14, 71, 123, 12, -14, 5, 5, -75, 12, -1, 51, 12, 61, -61, -13 };
        int n = arr.size();
        for (int i = 0; i < n-1; i++)
        {
            for (int j = 0; j < n-1; j++)
            {
                if ( arr[j] < arr[j + 1] ) 
                {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
                else if ( arr[j] == arr[j + 1])
                {
                    for (int a = j + 1; a < n - 1; a++)
                    {
                        arr[a] = arr[a + 1];
                    }
                }
            }
        }
        for (int i : arr)
        {
            cout << i << endl;
        }

Upvotes: 0

Enrico
Enrico

Reputation: 120

Consider the following fragment of your code:

        for (int j=0;j<n;j++)
        {
            if (arr[j] < arr[j + 1])

What will happen on the last loop iteration, when j = n - 1?

Upvotes: 2

Rohan Bari
Rohan Bari

Reputation: 7726

You are trying to access out-of-bound array with this line:

arr[j + 1] AND arr[a + 1]

because it is iterating only till n. In the last valid iteration, the program tries to obtain the value of j + 1th and n + 1th indices respectively whereas the size of the array is n.

To solve this issue, you need to iterate till n - 1 condition. Just replace those n contained in the nested two For loops so that it will correctly iterate till the end of the loop.

Upvotes: 0

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