How to make it work faster?

Question

This code erases unnecessary gap between the symbols.
For example :
Input: abc de f .
Output: abc de f .
#include <iostream>
#include <string>
using namespace std;
string delUnnecessary (string &str)
{
int size = str.length();
for(int j = 0; j<=size; j++)
{
for(int i = 0; i <=j; i++)
{
if(str[i] == ' ' && str[i+1] == ' ')
{
str.erase(str.begin() + i);
}
else if(str[0]== ' ')
{
str.erase(str.begin());
}
else if(str[i] == '\0' && str[i-1]== ' ')
{
str.erase(str.end() - 1);
}
}
}
return str;
}
int main(){
ios_base::sync_with_stdio(0);
freopen("trim.in","r",stdin);
freopen("trim.out","w",stdout);
string s;
getline(cin,s);
cout«delUnnecessary(s);
return 0;
}

Answer 1

Here you can read the answer. Its to much to write it all down here ;)

https://www.google.com/amp/s/www.techiedelight.com/remove-whitespaces-string-cpp/amp/

Answer 2

Dragonxiv , thank you!