Shorten the string which same adjacent characters

stack.cpp

#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
#include <stack>
using namespace std;

// logic is each time character is pushed over stack will be checked with following character if it same continue else print the char

void calculate(string str){
    
    stack<char> s;
   
    for(int i=0;i<str.length();i++)
    {
        s.push(str.at(i));
        if(s.top()=str.at(i+1))
        { 
            s.pop();            
            continue;
        }
        else //not equal
        {
            char x= s.top();
            cout<< x <<endl;
            s.pop();
        }      
        s.push(str.at(i));
    }
    
}
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int t;
    while(t--){
    string str;
        cin>>str;
        calculate(str);   
    }
    return 0;
}