Templates - string - KMP algorithm

int pi[1005];
void GetPrefixFunction(char *s, int sl) {
    pi[0] = 0, pi[1] = 0;
    for(int i = 1, k = 0; i < sl; ++i) {
        while(k && s[i] != s[k])
            k = pi[k];
        pi[i + 1] = (s[i] == s[k]) ? ++k : 0;
    }
}

//返回t在s中所有occurrence的首地址，s和t都是从0开始的
int ans[1005], atop;
void KMP(char *s, int sl, char *t, int tl) {
    GetPrefixFunction(t, tl);
    atop = 0;
    for(int i = 0, k = 0; i < sl; ++i) {
        while(k && s[i] != t[k])
            k = pi[k];
        k += (s[i] == t[k]);
        if(k == tl)
            ans[++atop] = i - tl + 1;
    }
}