Trie树的简单介绍和应用

简单介绍http://www.cnblogs.com/cherish_yimi/archive/2009/10/12/1581666.html

应用http://www.cnblogs.com/cherish_yimi/archive/2009/10/12/1581795.html

#include <iostream>
#include <string>
#include <vector>
#include <cstdlib>
#include <map>
#include <list>
#include <algorithm>
#include <cstring>
#include <string.h>

using namespace std;

const int branchNum = 26; //声明常量
int i;

struct Trie_node {
    bool isStr; //记录此处是否构成一个串。
    Trie_node *next[branchNum]; //指向各个子树的指针,下标0-25代表26字符
    Trie_node() :
            isStr(false) {
        for (int i = 0; i < branchNum; i++)
            next[i] = NULL;
    }
};

class Trie {
public:
    Trie();
    void insert(const char* word);
    bool search(char* word);
    void deleteTrie(Trie_node *root);
    bool pre_char(bool judge, Trie_node* top);
public:
    Trie_node* root;
};

Trie::Trie() {
    root = new Trie_node();
}

void Trie::insert(const char* word) {
    Trie_node *location = root;
    while (*word) {
        if (location->next[*word - 'a'] == NULL) //不存在则建立
        {
            Trie_node *tmp = new Trie_node();
            location->next[*word - 'a'] = tmp;
        }
        location = location->next[*word - 'a']; //每插入一步，相当于有一个新串经过，指针要向下移动
        word++;
    }
    location->isStr = true; //到达尾部,标记一个串
}

bool Trie::search(char *word) {
    Trie_node *location = root;
    while (*word && location) {
        location = location->next[*word - 'a'];
        word++;
    }
    return (location != NULL && location->isStr);
}

void Trie::deleteTrie(Trie_node *root) {
    for (i = 0; i < branchNum; i++) {
        if (root->next[i] != NULL) {
            deleteTrie(root->next[i]);
        }
    }
    delete root;
}

bool Trie::pre_char(bool judge, Trie_node* top) {
    bool tmpjud, res;
    res = false;
    if (top->isStr && judge)
        return true;
    tmpjud = judge || top->isStr;
    for (int i = 0; i < branchNum; i++) {
        if (top->next[i] != NULL)
            res = res || pre_char(tmpjud, top->next[i]);
    }
    return res;
}

int main() //简单测试
{
    Trie t;
    t.insert("a");
    t.insert("abandon");
    char * c = "abandoned";
    t.insert(c);
    t.insert("abashed");
    if (t.search("abashed"))
        cout << "true\n";
    if (t.pre_char(false, t.root))
        cout << "yes\n";
    else
        cout << "no\n";
    return 0;
}