POJ 2001-Shortest Prefixes(Trie 入门)

题意：给你一组串，求每个串在组中唯一标志的最短前缀

分析：保存树上经过各节点的单词个数，扫描每个串当经过节点单词个数是一（能唯一标志）结束

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<11
#define All 1,N,1
#define read freopen("in.txt", "r", stdin)
#define N 20010
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
struct Trie{
    int ch[N][27];
    int val[N],num;
    void init(){
        num=1;
        memset(ch[0],0,sizeof(ch[0]));
    }
    int idx(char c){return c-'a';}
    //建树
    void build(char *s){
        int u=0,n=strlen(s);
        for(int i=0;i<n;++i){
            int v=idx(s[i]);
            if(!ch[u][v]){
                memset(ch[num],0,sizeof(ch[num]));
                ch[u][v]=num++;
            }
            u=ch[u][v];
            val[u]++;
        }
    }
    //查询
    void query(char *s){
        int u=0,n=strlen(s);
        for(int i=0;i<n;++i){
            int v=idx(s[i]);
            u=ch[u][v];
            printf("%c",s[i]);
            if(val[u]==1){
                break;
            }
        }
        printf("\n");
    }
}trie;
int main()
{
    trie.init();
    char a[1010][30];
    int id=0;
    while(~scanf("%s",a[id])){
        trie.build(a[id]);
        id++;
    }
    for(int i=0;i<id;++i){
        printf("%s ",a[i]);
        trie.query(a[i]);
    }
return 0;
}