Z algorithm

#include<bits/stdc++.h>
#define maxm 10001

using namespace std;

int L, R, k;
string str, patt, S;

void calculateZ(){
    vector<int> Z(S.size());
    L = R = 0;
    for(int i=1; i<S.size(); ++i){
        if(i > R){
            L = R = i;
            while(R < S.size() && S[i] == S[R-L]){
                R++;
            }
            Z[i] = R - L;
            R--;
        }
        else{
            k = i - L;
            if(Z[k] < R - i + 1){
                Z[i] = Z[k];
            }
            else{
                while(R < S.size() && S[i] == S[R-L]){
                    R++;
                }
                Z[i] = R - L;
                R--;
            }
        }
    }
    cout<<"Z = ";
    for(int i=0; i<S.size(); ++i)
        cout<<Z[i]<<" ";
    cout<<"\nPositions in string:\n";
    for(int i=patt.size()+1; i<S.size(); ++i)
        cout<<Z[i]<<" ";
    cout<<"\n";
}


int main(){
    S="";
    cin>>str>>patt;
    S += patt + "$" + str;
    calculateZ();
    return 0;
}