Longest Even Length Substring

PROBLEM :

For given string ‘str’ of digits, find length of the longest substring of ‘str’, such that the length of the substring is 2k digits and sum of left k digits is equal to the sum of right k digits.


Input:

The first line of input contains an integer T denoting the number of test cases. The description of T test cases follows.
Each test case contains a string str of length N.

Output:

Print the resultant substring of length 2k such that sum of left k elements is equal to right k elements and if there is no such substring print 0.


Constraints:

1 = T = 100
1 = N = 100
0 = k = 100

Example:

Input:
2
000000
1234123

Output:
6
4

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SIMPLE c++ IMPLEMENTATION :
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#include<iostream>
using namespace std;
#include<string.h>
int Longest_Even_Length_Substring(string ) ;
int max(int ,int ) ;

int main()
 {
int t,ans ;
string str ;
cin>>t ;
while(t--)
{
   cin>>str ;
 
   ans=Longest_Even_Length_Substring(str) ;
   cout<<ans<<endl ;
}
return 0;
}

int Longest_Even_Length_Substring(string str)
{
    int len ;
    len=str.length() ;
   
    int i,lsum,rsum,l,r,ans ;
    ans=0 ;
    for(i=0;i<len-1;i++)
    {
        l=i ;
        r=i+1 ;
       
        lsum=0 ;
        rsum=0 ;
       
        while(l>=0&&r<len)
        {
            lsum=lsum+(str[l]-'0') ;
            rsum=rsum+(str[r]-'0') ;
           
            if(lsum==rsum)
                ans=max(ans,r-l+1) ;
               
            l-- ;
            r++ ;
        }
    }
    return ans ;
}

int max(int a,int b)
{
    return a>b?a:b ;
}

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