# How to solve this using Z algo , help needed. [Codeforces Beta Round #93 (Div. 1 Only)]

Question : “https://codeforces.com/contest/126/problem/B

How to solve this using Z algo I make Z array but after that I m stuck , i have no clue how to do in editorial they simply write this can be done by Z algo .

Please explain @galencolin @ay2306 (I saw your code too , can u explain please ) @ssjgz @everule1 @hetp111

@ay2306 's solution -

``````vector<int> z_val(string &a){
int n = a.size();
vector<int> z(n,0);
int L = 0, R = 0;
for(int i = 0; i < n ; ++i){
if(i > R){
L = R = i;
while(R < n && a[R-L] == a[R])R++;
z[i] = R-L; R--;
}else{
int k = i-L;
if(z[k] < R-i+1)z[i]=z[k];
else{
L=i;
while(R < n && a[R-L] == a[R])R++;
z[i] = R-L; R--;
}
}
}
return z;
}

int main(){
string a;
cin >> a;
auto z = z_val(a);
int ans = 0;
int n = a.size(),maxz=0;
for(int i = 0; i < n; ++i){
if(z[i] <= ans)continue;
if(maxz >= n-i && z[i] == n-i){
printf("index = %d, char = %c, z[i] = %d\n",i,a[i],z[i]);
ans = n-i; break;
}
maxz = max(maxz,z[i]);
}
if(ans == 0)cout << "Just a legend";
else for(int i = 0; i < ans; ++i)cout << a[i];
}
``````

After Z algo what u did ? I don’t know -

Ex : “f i x p r e f i x s u f f i x”
Z - 0 0 0 0 0 03 0 0 0 0 1 3 0 0

Then ?