Longest_palindromic_substring(GFG)(very imp).cpp

//{ Driver Code Starts
//Initial template for C++

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

// } Driver Code Ends
//User function template for C++

class Solution{   
public:
    string longestPalindrome(string s){
        string str="";
        int n=s.length();
        
        //iterate over the string
        for(int i=0;i<n;i++){
            
            //initialize two pointer
            int left=i, right=i;
            
            
            // expand the range of palindrome,
            // while two pointers are same 
            
            while(left>=0 && s[left]==s[i])left--;
            while(right<n && s[right]==s[i])right++;
            
            // expand the range of palindrome,
            // while two pointers are same 
            
            while(left>=0 && right<n && s[left]==s[right]){
                left--;
                right++;
            }
            
            // get the substring that is palindrome
            string candidate = s.substr(left+1, right-left-1);
            // now check,
            // if current palindrome is longer than the previous one
            if(candidate.length()>str.length()){
                str=candidate;
            }
        }
        return str;
    }
};

//{ Driver Code Starts.



int main(){
    int t;
    cin>>t;
    while(t--){
        string S;
        cin>>S;
        Solution ob;
        cout<<ob.longestPalindrome(S)<<endl;
    }
    return 0;
}

// } Driver Code Ends