HDU 1671 Phone List（字典树）

最新推荐文章于 2024-08-15 02:19:57 发布

Spectacules

最新推荐文章于 2024-08-15 02:19:57 发布

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分类专栏： ACM__普通数据结构

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本文介绍了一种使用字典树（Trie）来判断电话号码列表中是否存在号码互为前后缀的情况的方法，通过示例展示了如何实现这一算法。

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Phone List

Problem Description

Given a list of phone numbers, determine if it is consistent in the sense that no number is the prefix of another. Let’s say the phone catalogue listed these numbers:
1. Emergency 911
2. Alice 97 625 999
3. Bob 91 12 54 26
In this case, it’s not possible to call Bob, because the central would direct your call to the emergency line as soon as you had dialled the first three digits of Bob’s phone number. So this list would not be consistent.

Input

The first line of input gives a single integer, 1 <= t <= 40, the number of test cases. Each test case starts with n, the number of phone numbers, on a separate line, 1 <= n <= 10000. Then follows n lines with one unique phone number on each line. A phone number is a sequence of at most ten digits.

Output

For each test case, output “YES” if the list is consistent, or “NO” otherwise.

Sample Input

Sample Output

NO
YES

【思路分析】
裸的字典树，只不过字母为0~9这十个数字。

代码如下：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
#define MAX 10
#define maxn 10005
char phoneNum[maxn][15];
char num[15];
struct Trie
{
    bool flag;//标记从根到此是否为一个单词
    Trie *next[MAX];
};
Trie *root;

void init()
{
    root = (Trie *)malloc(sizeof(Trie));
    root->flag = false;
    for(int i = 0;i < MAX;i++)
    {
        root->next[i] = NULL;
    }
}
void inserting(char *word)
{
    Trie *temp = root;
    while(*word != '\0')
    {
        if(temp->next[*word - '0'] == NULL)//若不存在该字母，插入之
        {
            Trie *cur = (Trie *)malloc(sizeof(Trie));
            for(int i = 0;i < MAX;i++)
            {
                cur->next[i] = NULL;
            }
            cur->flag = false;
            temp->next[*word - '0'] = cur;//在该字母下新建10个节点，以便继续插入，构成单词
        }
        temp = temp->next[*word - '0'];
        word++;
    }
    temp->flag = true;//到此为一个单词
}
bool searching(char *word)
{
    Trie *temp = root;
    while(*word != '\0')
    {
        if(temp == NULL || temp->next[*word - '0'] == NULL)//不存在该字母
            return 0;
        temp = temp->next[*word - '0'];
        word++;
    }
    return temp->flag;
}
void deleting(Trie *cur)
{
    for(int i = 0;i < MAX;i++)
    {
        if(cur->next[i] != NULL)
        {
            deleting(cur->next[i]);
        }
    }
    free(cur);
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        init();
        int n;
        bool flag = true;
        scanf("%d",&n);
        for(int i = 0;i < n;i++)
        {
            scanf("%s",phoneNum[i]);
            inserting(phoneNum[i]);
        }
        for(int i = 0;i < n;i++)
        {
            int len = strlen(phoneNum[i]);
            memset(num,'\0',sizeof(num));
            for(int j = 0;j < len - 1;j++)
            {
                num[j] = phoneNum[i][j];
                if(searching(num))//存在该单词前缀
                {
                    flag = false;
                    break;
                }
            }
            if(flag == false)
            {
                break;
            }
        }
        if(flag)
            printf("YES\n");
        else
            printf("NO\n");
        deleting(root);
    }
    return 0;
}