hdu1247 hat's words 字典树

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/*    题目描述：给出n（n<5,000）个单词，其中被称为hatword的单词满足这个词恰好由给出的词中的两个单词                    首位相接而成，现要求输出给出单词中的hatword            方法：应用字典树解决问题，先将单词全部插入完成建树，然后利用dfs进行查询，具体查询方式见注释*/#pragma warning(disable:4786)#pragma comment(linker, "/STACK:102400000,102400000")#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<stack>#include<queue>#include<map>#include<set>#include<vector>#include<cmath>#include<string>#include<sstream>#define LL long long#define FOR(i,f_start,f_end) for(int i=f_start;i<=f_end;++i)#define mem(a,x) memset(a,x,sizeof(a))#define lson l,m,x<<1#define rson m+1,r,x<<1|1using namespace std;const int INF = 0x3f3f3f3f;const int mod = 1e9 + 7;const double PI = acos(-1.0);const double eps=1e-8;const int maxn = 100 + 5;const int maxnode = 5e4 + 5;const int sigma_size = 26;char s[maxnode][maxn];struct Trie{    int ch[maxnode][sigma_size];    int val[maxnode];    int sz;    Trie()  { sz = 1;       mem(ch , 0);  }    int idx(char c)     {return c - 'a';}    void insert(char *s ,int v)    {        int u = 0 , n = strlen(s);        for(int i = 0 ; i<n ; i++){            int c = idx(s[i]);            if(!ch[u][c]){                mem(ch[sz] , 0);                val[sz] = 0;                ch[u][c] = sz++;            }            u = ch[u][c];        }        val[u] = v;    }    bool 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 false;            u = ch[u][c];        }        if(!val[u])     return false;        return true;    }    bool dfs(char * s , int sum)    {        if(sum==1){            if(find(s))     return true;            else             return false;        }        int u = 0 , n = strlen(s);        for(int i = 0 ; i<n ; i++){            int c = idx(s[i]);            u = ch[u][c];            if(i!=n-1&&val[u]!=0&&dfs(s+i+1 , sum + 1))  //前两个条件指s[0]——s[i]构成的单词在trie里，后一条件指s[i+1]——s[n-1]在trie里                return true;        }        return false;    }};Trie t;int main(){    int n = 1;    while(scanf("%s",s[n])!=EOF){        t.insert(s[n++] , 1)  ;    }    for(int i  = 1 ; i < n ; i++){        if(t.dfs(s[i] , 0))    printf("%s\n",s[i]);    }    return 0;}
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