Knuth-Morris-Pratt algorithm

#include <cstdio>
#include <iostream>
#include <vector>
using namespace std;
vector <int> prefixFunction(string text)
{
    int k, i, len = text.length();
    vector <int> p(len);
    for(i = 1; i < len; i++)
    {
        while(k > 0 && text[i] != text[k]) k = p[k - 1];
        if(text[i] == text[k]) k++;
        p[i] = k;
    }
    return p;
}
int main()
{
    string text, pattern;
    cin >> text >> pattern;
    text = pattern + '$' + text;
    vector <int> p = prefixFunction(text);
    int len = pattern.length(), i;
    for(i = 0; i < p.size(); i++) if(p[i] == len) printf("%d ", i - 2 * len);
    return 0;
}