hdu 1251（字典树） 统计难题 http://acm.hdu.edu.cn/showproblem.php?pid=1251
解题思路：直接套用字典树的模板，注意以空行结束的判断是 strcmp(str,"")==0
代码：
#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
//创建一个字典树结构体
struct node{
int num;
struct node *br[26];
};
node *root;
//插入字母建立树
void Tree_Insert(char str[]){
node *t , *s = root;
int i , j;
int len = strlen(str) - 1;
for(i = 0 ;i <= len ; i++){
int id = str[i] - 'a';
if(s -> br[id] == NULL){
t = new node;
for(j = 0 ; j <= 25 ; j++){
t -> br[j] = NULL;
}
t -> num = 0;
s -> br[id] = t;
}
s = s -> br[id];
s ->num++;
}
}
//查找
int Tree_search(char str[]){
node *s = root;
int count;
int len = strlen(str) - 1;
for(int i = 0 ; i <= len ; i++){
int id = str[i] - 'a';
if(s -> br[id] == NULL){
count = 0;
return count;
}
else{
s = s -> br[id];
count = s -> num;
}
}
return count;
}
int main(){
int i , j;
root = new node;
for(i = 0 ; i <= 25 ; i++){
root -> br[i] = NULL;
root -> num = 0;
}
char str[15];
while(gets(str),strcmp(str,"")){ //注意这里的判断条件，逗号表达式
Tree_Insert(str);
}
while(gets(str)){
cout<<Tree_search(str)<<endl;
}
return 0;
}
