Longest Palindrome in a String

PROBLEM :
Given a string S, find the longest palindromic substring in S.

Substring of string S:
S[ i . . . . j ] where 0 = i = j < len(S)

Palindrome string:
A string which reads the same backwards. More formally, S is palindrome if reverse(S) = S.
Incase of conflict, return the substring which occurs first ( with the least starting index ).

Input:
The first line of input consists number of the test cases. The following T lines consist of a string each.

Output:
In each separate line print the longest palindrome of the string given in the respective test case.

Constraints:
1 =T= 100
1 = str= 100

Example:
Input:
1
aaaabbaa

Output:
aabbaa

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SIMPLE c++ IMPLEMENTATION : DP solution O(n^2)
--------------------------------------------------------------------------------

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

string GetSubString(string str,int start,int end){
        if(start==end)
            return "" ;
           
        string s="" ;
       
        for(int i=start;i<=end;i++)
            s=s+str[i] ;
           
        return s ;
    }
   
string longestPalindrome(string str) {
        if(str.length()==0)
            return "" ;
           
        string STR=str ;
        bool dp[str.length()][str.length()] ;
        string palindromSTR ;
        int i,j,k ;
       
        for(i=0;i<str.length();i++)
            for(j=0;j<str.length();j++)
                dp[i][j]=false ;
               
        for(i=0;i<str.length();i++)
            dp[i][i]=true ;
        palindromSTR=str[0] ;
           
        for(i=0;i<str.length()-1;i++)
            if(str[i]==str[i+1]){
            dp[i][i+1]=true ;
            if(GetSubString(str,i,i+1).length()>palindromSTR.length())
               palindromSTR=GetSubString(str,i,i+1) ;
}
               
        for(k=2;k<str.length();k++){
            for(i=0;i<str.length()-k;i++){
                j=i+k ;
                if(str[i]==str[j]&&dp[i+1][j-1]==true){
                    if(GetSubString(str,i,j).length()>palindromSTR.length())
                        palindromSTR=GetSubString(str,i,j) ;
                    dp[i][j]=true ;
                }
            }
        }
        return palindromSTR ;
    }

int main()
{
int t ;
cin>>t ;
while(t--)
{
   string str ;
   cin>>str ;
 
   cout<<longestPalindrome(str)<<endl ;
}
return 0;
}

--------------------------------------------------------------------------------
SIMPLE c++ IMPLEMENTATION :  O(n^2)
--------------------------------------------------------------------------------

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

void PrintString(string str,int start,int end){
        for(int i=start;i<=end;i++)
            cout<<str[i] ;
        cout<<endl ;
    }

void longestPalindrome(string str) {
    int start=0;
    int maxlen=1 ;
    int len=str.length() ;
    int low,high ;
   
    for(int i=1;i<len;i++)
    {
        low=i-1 ;
        high=i ;
       
        while(low>=0&&high<len && str[low]==str[high])
        {
            if(high-low+1>maxlen)
            {
                start=low ;
                maxlen=high-low+1 ;
            }
            low-- ;
            high++ ;
        }
       
        low=i-1 ;
        high=i+1 ;
       
        while(low>=0&&high<len && str[low]==str[high])
        {
            if(high-low+1>maxlen)
            {
                start=low ;
                maxlen=high-low+1 ;
            }
            low-- ;
            high++ ;
        }
    }
   
    PrintString(str,start,start+maxlen-1) ;
    }

int main()
{
int t ;
cin>>t ;
while(t--)
{
   string str ;
   cin>>str ;
 
   longestPalindrome(str) ;
}
return 0;
}

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