hdu 1251 统计难题 (前缀树)

题意是：



Ignatius最近遇到一个难题,老师交给他很多单词(只有小写字母组成,不会有重复的单词出现),现在老师要他统计出以某个字符串为前缀的单词数量(单词本身也是自己的前缀).

思路很简单，前缀数组入门题，对于每个结点，用val数组记录当前字符串为前缀的字符串数量，之后就是插入，查询操作了

代码如下：

#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
using namespace std;
#define LL long long
const int maxnode = 1000000 ;
const int sigma_size = 26; 

struct Trie {
	int ch[maxnode][sigma_size];
	int val[maxnode];
	int sz;
	Trie() { sz = 1; memset(ch[0], 0, sizeof(ch[0]));};
	int idx(char c) {return c - 'a';}

	void insert(char *s) {
		int u = 0, n = strlen(s);
		for(int i = 0; i < n; i++) {
			int c = idx(s[i]);
			if(!ch[u][c]) {
				memset(ch[sz], 0, sizeof(ch[sz]));
				val[sz] = 1;
				ch[u][c] = sz++;
			}
			else val[ch[u][c]]++;
			u = ch[u][c];
		}
	}

	int find(char *s) {
		int u = 0, n = strlen(s);
		for(int i = 0; i < n; i++) {
			int c = idx(s[i]);
			if(!ch[u][c]) return 0;
			else u = ch[u][c];
		}
		return val[u];
	}
};
Trie trie; 

int main() {
		char dic[11], qry[11];
		//freopen("input.txt", "r", stdin);
		while(gets(dic) && strcmp(dic, "") != 0) {
		//	printf("%s\n", dic);
			trie.insert(dic);
		}
		while(gets(qry)) printf("%d\n", trie.find(qry));
		return 0;
}