1047.Remove_All_Adjacent_Duplicates_In_String.cpp

/*
    written by Pankaj Kumar.
    country:-INDIA
    Institute: National Institute of Technology, Uttarakhand
*/
typedef long long ll ;
typedef unsigned long long ull;
typedef vector<int> vl;
typedef vector<vector<ll>> vvl;
/*  Abbrevations  */
#define ff first
#define ss second
#define mp make_pair
#define pb push_back
#define Endl "\n"
#define all(V) (V).begin(),(V).end()
#define srt(V) sort(all(V))
#define srtGreat(V) sort(all(V),greater<ll>())
// some extra
#define printv(v) for(ll i=0;i<ll(v.size());i++){cout<<v[i]<<" ";} cout<<endl;
#define precision(x) cout<<fixed<<setprecision(x);
#define sz(V) ll(V.size())

/* ascii value 
A=65,Z=90,a=97,z=122
*/
/* Some syntax 
//Syntax to create a min heap for priority queue
//priority_queue <int, vector<int>, greater<int>>pq;
*/


/*  --------------------MAIN PROGRAM----------------------------*/
// to run ctrl+b
const ll INF=1e18;
const ll mod1=1e9+7;
const ll mod2=998244353;

// Techniques :
// divide into cases, brute force, pattern finding
// sort, greedy, binary search, two pointer
// transform into graph

// Experience :
// Cp is nothing but only observation and mathematics.

// add main code here
class Solution {
public:
    string removeDuplicates(string s) {
        stack<char> st;
        string ans="";
        for(auto x:s){
            if(sz(st)==0){
                st.push(x);
            }
            else{
                if(st.top()==x){
                    st.pop();
                }
                else{
                    st.push(x);
                }
            }
        }
        while(sz(st)){
            ans+=st.top();
            st.pop();
        }
        reverse(all(ans));
        return ans;
    }
};



/* -----------------END OF PROGRAM --------------------*/
/*
* stuff you should look before submission 
* constraint and time limit
* int overflow
* special test case (n=0||n=1||n=2)
* don't get stuck on one approach if you get wrong answer
*/