2013
11-13

# Phone List

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:

• Emergency 911
• Alice 97 625 999
• 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.

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.

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

2
3
911
97625999
91125426
5
113
12340
123440
12345
98346

NO
YES

import java.util.Scanner;

public class Main {
private static Trie trie = new Trie();
private static boolean isConsistent = true;

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int t = sc.nextInt();
for (int i = 0; i < t; ++i) {
int n = sc.nextInt();
sc.nextLine();
trie = new Trie();
isConsistent = true;
for (int j = 0; j < n; ++j) {
String phone = sc.nextLine();
if (isConsistent)
buildTrie(phone);
}
if (isConsistent)
System.out.println("YES");
else
System.out.println("NO");
}
}

static void buildTrie(String s) {
// char[] c = s.toCharArray();
int len = s.length();
Trie tmpTrie = trie;
for (int i = 0; i < len; ++i) {
int ch = Integer.parseInt(s.substring(i, i + 1));
// System.out.println(ch+"---"+(int)ch);
Trie tmp = tmpTrie.next[ch];
if (tmp == null) {
tmp = new Trie();
tmp.node = 1;
if (i == len - 1)
tmp.isDispear = true;// 琛ㄧず杩��涓�釜�佃����灏�
tmpTrie.next[ch] = tmp;
tmpTrie = tmp;
} else {
if (tmp.isDispear) {
isConsistent = false;
break;
}

if (i == len - 1) {
isConsistent = false;
break;
}
tmpTrie = tmp;
}
}
}

private static class Trie {
int node = 0;
boolean isDispear = false;//������涓��璇��������涓�釜
Trie[] next = new Trie[10];
}
}