hihoCoder #1014 : Trie树

小白做题系列。

原题传送门

Code

////  main.cpp//  Algorithm_OJ2////  Created by PTkin_Wang on 16/3/25.//  Copyright © 2016年 PTkin_Wang. All rights reserved.//#include <iostream>#include <string.h>using namespace std;class Node {public :    int  count;    char letter;    bool exist_sub_node[26];    Node *sub_node[26];    Node() {        count  =  0 ;        letter = '0';        memset(exist_sub_node, 0, 26);        memset(sub_node,       0, 26);    }    void insert(string str) {        ++count;        if (0 == str.length())            return;        int index = str[0] - 'a';        if (!exist_sub_node[index]) { // not exist            Node *nextNode   = new Node();            nextNode->letter = str[0];            exist_sub_node[index] = true;            sub_node[index]       = nextNode;        }        sub_node[index]->insert(str.substr(1, str.size() - 1));    }};void check(string str, Node *node) {    if (0 == str.length()) {        cout << node->count;        return;    }    int index = str[0] - 'a';    if (!node->exist_sub_node[index]) {        cout << '0';    }    else {        check(str.substr(1, str.size() - 1), node->sub_node[index]);    }}int main(int argc, const char * argv[]) {    Node *root = new Node();    int    input_num;    string input_word;    cin >> input_num; // number of words in the dictionary    for (int i = 0; i < input_num; ++i) {        cin >> input_word;        root->insert(input_word);    }    cin >> input_num; // number of words to be checked    for (int i = 0; i < input_num; ++i) {        cin >> input_word;        check(input_word, root);        if (i != input_num - 1)            cout << endl;    }    return 0;}

Note

要得到 string 类型的长度应该使用 .size() 而不是 sizeof()

太久没写 C++ 都不熟悉了，误以为 sizeof(string) 可以得到字符串的长度，实际上如果要得到 string 的长度应该使用 string.size() ：）。

string 的本质是一个类，调用对象方法可以得到它的字符串长度，而使用 sizeof(string) 只能得到这个对象的大小，里面实际存储的包括了一个指向堆内的字符串的指针。

尝试一下下面代码：

#include <iostream>using namespace std;void output(string str) {    cout << "str = \"" << str << "\"" << endl         << "sizeof(\"" << str << "\") = " << sizeof(str) << endl         << "\"" << str << "\".size() = " << str.size() << "\n\n";}int main(int argc, const char * argv[]) {    string str1 = "ddd";    string str2 = "asudfghasodhsdf";    string str3 = "asudfghasodhfauosdfalsdfasudfgodhfauosdfa";    output(str1);    output(str2);    output(str3);    return 0;}

将会输出

str = "ddd"sizeof("ddd") = 24"ddd".size() = 3str = "asudfghasodhsdf"sizeof("asudfghasodhsdf") = 24"asudfghasodhsdf".size() = 15str = "asudfghasodhfauosdfalsdfasudfgodhfauosdfa"sizeof("asudfghasodhfauosdfalsdfasudfgodhfauosdfa") = 24"asudfghasodhfauosdfalsdfasudfgodhfauosdfa".size() = 41