KMP Optimized

#include <bits/stdc++.h>
#define MAXN 2000001
using namespace std;

int fail[MAXN];

void failFunc(string &p){
    int n = p.size();
    fail[0] = -1;
    for(int i = 0; i < n; i++){
        int node = fail[i];
        if(node >= 0 && p[node] != p[i]){
            node = fail[node];
        }
        fail[i+1] = node+1;
        if(p[i] == p[fail[i]]){
            fail[i] = fail[fail[i]];
        }
    }
}

void match(string &t, string &p){
    int i = 0, j = 0;
    while(i < (int) t.size()){
        while(j >= 0 && p[j] != t[i]){
            j = fail[j];
        }
        i++; j++;
        if(j == (int) p.size()){
            cout << i - p.size()  << endl;
        }
    }
}

int n;
string p,t;

int main(){
    bool can = 0;
    while(cin >> n){
        if(can) cout << endl;
        can = 1;
        cin >> p >> t;
        failFunc(p);
        match(t,p);
    }
    return 0;
}