Longest Even Length Substring

probelm id:--http://practice.geeksforgeeks.org/problems/longest-even-length-substring/0

code:--

#include <bits/stdc++.h>

using namespace std;
#define ll   long long
#define      pii               std::pair<int,int>
#define      vi                std::vector<int>
#define      vll               std::vector<long long>
#define      mp(a,b)           make_pair(a,b)
#define      pb(a)             push_back(a)
#define sc(x)   scanf("%d",&x)
#define scll(x)   scanf("%lld",&x)
#define sc2(x,y)   scanf("%d%d",&x,&y)
#define sc3(x,y,z)   scanf("%d%d%d",&x,&y,&z)
#define     pf(x)   printf("%d ",x)
#define     pf2(x,y)   printf("%d %d ",x,y)
#define     pf3(x,y,z)   printf("%d %d %d ",x,y,z)
#define pfnl   printf("\n");
#define      each(it,s)        for(auto it = s.begin(); it != s.end(); ++it)
#define      rep(i, n)         for(int i = 0; i < (n); ++i)
#define rep2(i,j,n)   for(int i = j; i < (n); ++i)
#define      fill(a)           memset(a, 0, sizeof (a))
#define      sortA(v)          sort(v.begin(), v.end())
#define      sortD(v)          sort(v.begin(), v.end(), greater<auto>())
#define      X                 first
#define      Y                 second

#define debug(x) cerr<<"debug->"<<#x<<"::"<<x<<endl
#define debug2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define debug3(x,y,z) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n"
#define MOD 1000000007

int main(int argc, char **argv) {
//std::ios::sync_with_stdio(false);
char str[105];
int t;
sc(t);
while(t--)
{
int ans=0;
cin>>str;
int n=strlen(str);
if(n==1) { pf(ans); pfnl; continue;  }
int k=(n&1)?n-1:n;
int h,s,e;//h means half of k
bool flag=0;
while(k)
{
h=k/2;
s=0,e=0;//s and e denotes start and end
rep(i,k) (i<h)?s+=str[i]-'0':e+=str[i]-'0';
if(s==e) { flag=1; break; }
for(int i=k;i<n;++i)
{
e+=str[i]-'0'   ,  e-=str[i-k/2]-'0';
s-=str[i-k]-'0' ,  s+=str[i-k/2]-'0';
if(s==e) { flag=1; break; }
}
if(flag) break;
k-=2;
}
if(flag) ans=k;
pf(ans);
pfnl;
}
return 0;
}