C++ random 0xC0000005 errors

Question

I made a program which converts n decimal numbers sk into other numerical system p but sometimes it crashes and the error code I get is 0xC0000005 (program still converts and outputs all the numbers) . One thing I just noticed that it happens then converted number is longer than 6 symbols (or it's just a coincidence).

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()
{
    long n,sk,p,j;
    string liekanos;
    ifstream f("u1.txt");
    f >> n;
    for (int i=0;i<n;i++)
    {
        f >> sk >> p;
        j=0;
        while (sk>0)
        {
            liekanos[j]=sk % p;
            sk/=p;
            j++;
        }
        for (j>=0;j--;)
        {
            if (liekanos[j]<10)
                cout<<int(liekanos[j]);
            else cout<<char(liekanos[j]+55);
        }
        cout<<endl;
    }
    return 0;
}

Example input:

3
976421618 7
15835 24
2147483647 2

Answer 1

With liekanos[j] you access element at index j but since you haven't specify size of this string, you are most likely trying to access non-existing element. You could call liekanos.resize(sk) before you enter your while loop to make sure it never happens.

Or if you know the maximum possible size of liekanos , you could declare it as string liekanos(N, c); where N is its size and c is the default value of each character in it.

Answer 2

您正在得到未定义的行为，因为liekanos字符串永远不会有任何大小或容量。

Answer 3

string liekanos;

By default string has zero size. But you try to

liekanos[j]=sk % p;

Answer 4

Better use std::vector<char> liekanos; instead of string liekanos; . You'll need to do some modifications in your code:

for (int i=0; i<n; i++)
{
    std::vector<char> liekanos;
    f >> sk >> p;
    while (sk>0)
    {
        liekanos.push_back(sk % p);
        sk/=p;
    }
    for (long j = liekanos.size(); j>=0; --j)
    {
        if (liekanos[j]<10)
            cout<<int(liekanos[j]);
        else cout<<char(liekanos[j]+'a');
    }
    cout<<endl;
}