HDU 1671 Phone List

Posted 2020-08-10 月夜下

Phone List

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 18202    Accepted Submission(s): 6115

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）

 

 

 

解析：字典树。

 

 

 

#include <iostream>
#include <cstring>
#include <string>
#include <algorithm>
using namespace std;

struct Node{
    Node* pt[10];
    bool isEnd;
};
Node* root;

int n;
string s[10005];
Node memory[100000];
int allo;

void trie_init()
{
    memset(memory, 0, sizeof(memory));
    allo = 0;
    root = &memory[allo++];
}

bool trie_insert(string& str)
{
    Node *p = root, *q;
    for(int i = 0; str[i] != ‘\0‘; ++i){
        int id = str[i]-‘0‘;
        if(p->pt[id] == NULL){
            q = &memory[allo++];
            p->pt[id] = q;
        }
        else{
            if(p->pt[id]->isEnd)
                return false;
        }
        p = p->pt[id];
    }
    p->isEnd = true;
    return true;
}

void solve()
{
    trie_init();
    bool ok = true;
    for(int i = 0; i < n; ++i){
        ok = trie_insert(s[i]);
        if(!ok){
            cout<<"NO"<<endl;
            return;
        }
    }
    cout<<"YES"<<endl;
}

bool cmp(const string& a, const string& b)
{
    return a.length() < b.length();
}

int main()
{
    int t;
    cin>>t;
    while(t--){
        cin>>n;
        for(int i = 0; i < n; ++i)
            cin>>s[i];
        sort(s, s+n, cmp);
        solve();
    }
    return 0;
}