HDU1671Phone List字典树应用详解

http://acm.hdu.edu.cn/showproblem.php?pid=1671

判断是否出现一个字符串的前缀

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 2 3 911 97625999 91125426 5 113 12340 123440 12345 98346   Sample Output NO YES   Source 2008 “Insigma International Cup” Zhejiang Collegiate Programming Contest - Warm Up（3）   Recommend lcy

#include<bits/stdc++.h>
using namespace std;
#define MAX 10
struct node
{
    int key;
    node *next[MAX];
    node()
    {
        key=0;
        for(int i=0; i<MAX; i++)
            next[i]=null;
    }
};
node *root;
void tireInsert(char *str)
{
    node*p=root,*q;
    for(int i=0; str[i]; i++)
    {
        int id=str[i]-'0';
        if(!p->next[id])
            p->next[id]=new node();//建立新节点;
        p=p->next[id];//p更新赋值为下一个节点
    }
    p->key=1;//把它的个数当做1
}
void dell(node*p)
{
    if(p)
    {
        for(int i=0; i<MAX; i++)
            if(p->next[i])
            {
                dell(p->next[i]);
                delete p->next[i];
            }
    }
}
int tireFind(char *str)
{
    node *p=root;
    int len=strlen(str);
    for(int i=0; str[i]; i++)
    {
        int id=str[i]-'0';
        p=p->next[id];//一个个节点开始找;
        if(!p)return 1;//说明不存在前缀;
        if(p->key==1&&i<len-1)return 0;//出现前缀,那么return 0;
        //i<len-1是保证不是他本身;
    }
    return 1;//无前缀则返回1；
}
int main()
{
    int N,T,i;
    char str[10005][11];
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&N);
        root=new node();//建立根节点;
        for(i=0; i<N; i++)
        {
            scanf("%s",str[i]);
            tireInsert(str[i]);//插入各个字符串;
        }
        for(i=0; i<N; i++)
            if(!tireFind(str[i]))
                break;
        printf(i<N?"NO\n":"YES\n");
        dell(root);//及时释放内存否则会超内存

    }
}