Unable to assign string to string data type in c++

Question

I'm trying to write a simple program to which takes away the spaces from a string as follows:

#include <iostream>
#include <bits/stdc++.h>
#include <strings.h>
#include <string>
using namespace std;

int main()
{
    string s;
    getline(cin,s);
    cout<< s;
    string c;
    int i =0,j=0;
    while(s[i]!='\0'){
        if(s[i] == ' ')
            i++;
        else{
            c[j] = s[i];
            j++;
            i++;
        }
    }
    c[j] ='\0';
    cout << c; //unable to print

 }

Here when I try to print c I can't seem to be able to get a result. When I used c as a character array it worked but I'd still like to know what I was doing wrong. Thanks so much

c is an empty string. If you want to add to it, use c += s[i]; You also do not need to null terminate it, and you would be better off using s.size() to know how long to iterate, or a range based for loop. — Retired Ninja
– Retired Ninja, Commented Aug 8, 2018 at 3:55
Off-topic, but what is "strings.h", and you should avoid using bits/stdc++, and instead just include what you need. — Tas
– Tas, Commented Aug 8, 2018 at 4:21

R Sahu · Accepted Answer · 2018-08-08 03:57:56Z

1

string c;

creates an empty string. After that,

c[j] = s[i];

is cause for undefined behavior.

You can solve the problem using many strategies. Here are a couple of them:

Construct `c` with large enough size

string c(s.size(), '\0');

Use `std::string::push_back`

Instead of

    c[j] = s[i];

    ...

c[j] ='\0';

use

    c.push_back(s[i]);

    ...

c.push_back('\0');

answered Aug 8, 2018 at 3:57

R Sahu

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Unable to assign string to string data type in c++

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Construct `c` with large enough size

Use `std::string::push_back`

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Construct c with large enough size

Use std::string::push_back

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Construct `c` with large enough size

Use `std::string::push_back`