51nod 1277字符串中的最大值（拓展kmp）

#include <iostream>
#include <cstring>
using namespace std;
const int maxn = 1e6 + 100;
char S[maxn];
int Next[maxn], extend[maxn];
void GetNext(char *T, int *Next){
    int len = strlen(T);
    Next[0] = len;
    int a, p;
    for(int i = 1, j = -1; i < len; i++, j--){
       if(j < 0 || i + Next[i-a] >= p){
            if(j < 0) p = i, j = 0;
            while(p < len && T[p] == T[j])
                p++, j++;
            Next[i] = j;
            a = i;
       } else Next[i] = Next[i-a];
    }
}
void GetExtend(char *S, char *T, int *extend, int *Next){
    GetNext(T, Next);
    int a, p;
    int slen = strlen(S), tlen = strlen(T);
    for(int i = 0, j = -1; i < slen; i++, j--){
        if(j < 0 || i + Next[i-a] >= p){
            if(j < 0) p = i, j = 0;
            while(p < slen && j < tlen && S[p] == T[j]) p++, j++;
            extend[i] = j;
            a = i;
        } else extend[i] = Next[i-a];
    }
}
int Num[maxn];
int main(){
    cin>>S;
    int len = strlen(S);
    GetNext(S, Next);
    for(int i = 0; i < len; i++) Num[Next[i]]++;
    long long ans = 0, n = 0;
    for(int i = len; i >= 1; i--){
        n += Num[i];
        ans = max(ans, n*i);
    }
    cout<<ans<<endl;
}