题意：有多少个字符串，能恰好被另外两个字符串拼接而成
一般查询某个字符串是否存在，，其实都能用hash水过去
思路：枚举字符串，再枚举哪两个字符串组成它，看这两个字符串是否存在
#include<cstdio>
#include<cmath>
#include<cstring>
#include<queue>
#include<vector>
#include<map>
#include<set>
#include<string>
#include<iostream>
#include<functional>
#include<algorithm>using namespace std;
typedef long long LL;
typedef pair<int, int> PII;const int MX = 1e5 + 5;
const int HS = 1000007;char word[MX][100];
int H_head[HS], H_next[MX], H_rear;int Hash(char*S) {int len = strlen(S), ret = 0;for(int i = 0; i < len; i++) {ret = ret * 131 + S[i];}return (ret & 0x7fffffff) % HS;
}void Hash_init() {H_rear = 0;memset(H_head, -1, sizeof(H_head));memset(H_next, -1, sizeof(H_next));
}bool Hash_query(char*S) {int h = Hash(S);for(int i = H_head[h]; ~i; i = H_next[i]) {if(strcmp(word[i], S) == 0) return true;}return false;
}void Hash_add(int id) {int h = Hash(word[id]);for(int i = H_head[h]; ~i; i = H_next[i]) {if(strcmp(word[i], word[id]) == 0) return;}H_next[id] = H_head[h];H_head[h] = id;
}int main() {//freopen("input.txt", "r", stdin);int tot = 0;Hash_init();while(~scanf("%s", word[tot])) {Hash_add(tot++);}char temp[100];for(int i = 0; i < tot; i++) {int L = strlen(word[i]);for(int j = 1; j < L; j++) {memcpy(temp, word[i], sizeof(char) * j);temp[j] = 0;if(Hash_query(temp) && Hash_query(word[i] + j)) {printf("%s\n", word[i]);break;}}}return 0;
}