HDU 1251 字典树(前缀树)

题目大意 ：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).(单词互不相同)

代码:

  #include<iostream>
  #include<cstdio>
  #include<cstdlib>
  #include<cstring>
  #include<queue>
  #include<algorithm>
  #include<cmath>
  #include<map>
  using namespace std;
  #define INF 0x7fffffff

  int ch[1000000][30],isword[1000000];
  int num[1000000],nz;

  void insert(char s[],int len){
      int i,j,u = 0;
      num[u]++;
      for(i=0;i<len;i++){
	      int v = s[i] - 'a' ;
	      if(!ch[u][v]){
		      memset(ch[nz],0,sizeof(ch[nz]));
		      isword[nz] = 0;
		      ch[u][v] = nz ++ ;
	      }
	      u = ch[u][v] ;
	      num[u]++;
      }
      isword[u] = 1;
  }

  int query(char s[]){
      int i,j,len,u = 0;
      len = strlen(s);
      for(i=0;i<len;i++){
              int v = s[i] - 'a';
	      if(!ch[u][v]){
		        return 0; 
	      }
	      u = ch[u][v];
      }
      return num[u];
  }

  int main(){
      int i,len;
      char s[12],c;
      nz = 1;
      memset(num,0,sizeof(num));
      memset(ch[0],0,sizeof(ch[0]));
      c = getchar();
      while(c != '\n'){
	      gets(s+1);
	      s[0] = c ;
	      len = strlen(s);
	      s[len] = '\0' ;
	      insert(s,len);
	      c = getchar();
      }

      while(scanf("%s",s) == 1){
	      int ans = query(s);
	      printf("%d\n",ans);
      }
      return 0;
  }