扩展KMP

#include <bits/stdc++.h>

using namespace std;

const int MAX_N  = 101010;

int next[MAX_N],extend[MAX_N];

void getnext(char *T) {
    int a = 0;
    int Tlen = strlen(T);
    next[0] = Tlen;

    while(a<Tlen-1&&T[a]==T[a+1]) a++;
    next[1] = a;

    a = 1;

    for(int k=2; k < Tlen; k++) {
        int p = a + next[a] - 1,L = next[k-a];
        if((k-1)+L>=p) {
            int j = (p-k+1) > 0 ? p - k + 1 : 0;
            while(k+j<Tlen&&T[k+j]==T[j])
                j++;
            next[k] = j;
            a = k;
        }
        else next[k] = L;
    }

}

void getextend(char *S,char *T) {
    int a = 0;
    getnext(T);

    int Slen = strlen(S);
    int Tlen = strlen(T);

    int MinLen = Slen < Tlen ? Slen : Tlen;
    while(a<MinLen&&S[a]==T[a]) a++;
    extend[0] = a;
    a = 0;

    for(int k=1; k < Slen; k++) {
        int p = a + extend[a] - 1,L = next[k-a];
        if((k-1)+L>=p) {
            int j = (p - k + 1) > 0 ？ p - k + 1:0;
            while(k+j<Slen&&j<Tlen&&S[k+j]==T[j]) j++;
            extend[k] = j;
            a = k;
        }
        else extend[k] = L;
    }

}