C++ string termination not happening ? Why? - c++

Question

#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
cin.ignore();
while(t--){
string s;
getline(cin,s);
int i =0;
int count =0;
while(i<s.size()){
if(s[i]!=' '){
//cout<<count<<":";
s[count++]=s[i];
}
i++;
}
s[count]='\0';
cout<<s<<endl;
}
return 0;
}
Why in the end String is not terminating with '\0'?
For Input:
2
geeks for geeks
g f g
your output is:
geeksforgeeksks
gfgg f g

Answer 1

To remove a character from a string, you should use erase.
See the remove-erase idiom.

Answer 2

std::string is not a C-style null terminated string (but you can obtain one from it). As such, inserting a null character will not terminate it. If you want to truncate a string from the end, you can simply resize() it. Otherwise, if you want to remove characters, you can erase() them.
You say you want to remove spaces. To do that with your existing code, simply replace s[count]='\0'; with s.resize(count);, eg:
#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin >> t;
cin.ignore();
while (t--){
string s;
getline(cin, s);
int i = 0;
int count = 0;
while (i < s.size()){
if (s[i] != ' '){
//cout<<count<<":";
s[count++] = s[i];
}
i++;
}
s.resize(count);
cout << s << endl;
}
return 0;
}
However, a better way to handle this would look more like this:
#include <iostream>
#include <string>
int main()
{
int t;
std::cin >> t;
std::cin.ignore();
while (t--){
std::string s;
std::getline(cin, s);
std::string::size_type idx = 0;
while ((idx = s.find(‘ ‘, idx)) != std::string::npos){
s.erase(idx, 1);
}
std::cout << s << std::endl;
}
return 0;
}
Alternatively:
#include <iostream>
#include <string>
#include <algorithm>
int main()
{
int t;
std::cin >> t;
std::cin.ignore();
while (t--){
std::string s;
std::getline(cin, s);
std::string::iterator iter = std::remove(s.begin(), s.end(), ‘ ‘);
s.erase(iter, s.end());
std::cout << s << std::endl;
}
return 0;
}