HDU 1251 统计难题(Tire tree)

题目：

      给一个单词字典A={str[0], str[1], ...}，再给定一系列的单词B = {s[0], s[1], s[2], ...}, 求字典A中以s[i]为前缀的单词有多少。

解法：

      Tire tree, 先建字典数，然后再查询每个给定的单词。

AC代码如下：

/*Author; ACb0yDate: 2010年12月4日20:21:57ProblenID: HDU 1251 统计难题Type: Tir treeResult: 3280541 2010-12-04 20:18:55 Accepted 1251 140MS 43760K 1198 B G++ ACb0y */#include <stdio.h>#include <string.h>#include <malloc.h>struct node {node * child[26];int count;};node * root;void insert_tree(char * str) {node * pnew = NULL;node * cur = root;int length = strlen(str);for (int i = 0; i < length; ++i) {int pos = str[i] - 'a';if (cur->child[pos] == NULL) {pnew = (node *)malloc(sizeof(node));memset(pnew->child, 0, sizeof(node * [26]));pnew->count = 1;cur->child[pos] = pnew;cur = cur->child[pos];} else {cur->child[pos]->count++;cur = cur->child[pos];}}}int get_ans(char * str) {int length = strlen(str);node * cur = root;for (int i = 0; i < length; ++i) {int pos = str[i] - 'a';if (cur->child[pos] == NULL) {cur = cur->child[pos];break;} else {cur = cur->child[pos];}}return cur == NULL ? 0 : cur->count;}int main(){char str[11];#ifndef ONLINE_JUDGEfreopen("in.txt", "r", stdin);#endifroot = (node *)malloc(sizeof(node));memset(root->child, 0, sizeof(node * [26]));root->count = 0;while (gets(str)) {if (strcmp(str, "") == 0) {while (gets(str)) {printf("%d/n", get_ans(str));}} else {insert_tree(str);}}return 0;}