HDU 1671——Phone List(Trie树)
2014-10-08 21:11
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Phone List
Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 10865 Accepted Submission(s): 3746
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
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题目大意:
给你n个电话号码,判断存不存在某个电话号码是另外一个电话号码的前缀
思路:
基础的Trie树
但是有个特殊判断吧,插入某个电话号码的时候整个经过的全是之前已有的节点,那么也是某个电话号码的前缀
记得用递归写个删除,不然会爆内存
#include<iostream> #include<cstring> #include<cstdio> #include<algorithm> #include<cstdlib> const int maxn=10001; const int sigma_size=10; using namespace std; bool flag; struct Trie { int val; Trie *next[sigma_size]; Trie():val(0){memset(next,0,sizeof(next));} }; Trie *root; void insert(char *s) { Trie *p=root; int l=strlen(s); int cnt=0; flag=true; for(int i=0;i<l;++i){ int c=s[i]-'0'; if(p->next[c]==NULL){ p->next[c]=new Trie; p=p->next[c]; }else{ cnt++; p=p->next[c]; } if(p->val) flag=false; } p->val=1; if(cnt==l) flag=false; } void del(Trie *p) { for(int i=0;i<sigma_size;++i){ if(p->next[i]!=NULL){ del(p->next[i]); } } delete(p); } int main() { int T; cin>>T; while(T--){ root=new Trie; int n; scanf("%d",&n); char str[maxn]; flag=true; while(n--){ scanf("%s",str); if(flag){ insert(str); } } if(flag) printf("YES\n"); else printf("NO\n"); del(root); } return 0; }
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