Shortest Prefixes（trie树唯一标识）

Shortest Prefixes

Time Limit: 1000MS		Memory Limit: 30000K
Total Submissions: 15948		Accepted: 6887

Description

A prefix of a string is a substring starting at the beginning of the given string. The prefixes of "carbon" are: "c", "ca", "car", "carb", "carbo", and "carbon". Note that the empty string is not considered a prefix in this problem, but every non-empty string is considered to be a prefix of itself. In everyday language, we tend to abbreviate words by prefixes. For example, "carbohydrate" is commonly abbreviated by "carb". In this problem, given a set of words, you will find for each word the shortest prefix that uniquely identifies the word it represents.

In the sample input below, "carbohydrate" can be abbreviated to
"carboh", but it cannot be abbreviated to "carbo" (or anything shorter)
because there are other words in the list that begin with "carbo".

An exact match will override a prefix match. For example, the prefix
"car" matches the given word "car" exactly. Therefore, it is understood
without ambiguity that "car" is an abbreviation for "car" , not for
"carriage" or any of the other words in the list that begins with "car".

Input

The
input contains at least two, but no more than 1000 lines. Each line
contains one word consisting of 1 to 20 lower case letters.

Output

The
output contains the same number of lines as the input. Each line of the
output contains the word from the corresponding line of the input,
followed by one blank space, and the shortest prefix that uniquely
(without ambiguity) identifies this word.

Sample Input

carbohydrate
cart
carburetor
caramel
caribou
carbonic
cartilage
carbon
carriage
carton
car
carbonate

Sample Output

carbohydrate carboh
cart cart
carburetor carbu
caramel cara
caribou cari
carbonic carboni
cartilage carti
carbon carbon
carriage carr
carton carto
car car
carbonate carbona
题解：让找唯一能确定一个单词的前缀；我们想到当唯一确定的时候必定word[k]是1；那么很好解决了
代码：

 #include<iostream>
 #include<algorithm>
 #include<cstdio>
 #include<cstring>
 #include<cmath>
 #include<vector>
 #define mem(x,y) memset(x,y,sizeof(x))
 using namespace std;
 typedef long long LL;
 const int MAXN=;
 char s[][];
 int ch[MAXN][],word[MAXN];
 int sz;
 void initial(){
     sz=;
     mem(word,);
 }
 void insert(char *s){
     int len=strlen(s);
     int j,k=;
     for(int i=;i<len;i++){
         j=s[i]-'a';
         if(!ch[k][j]){
             mem(ch[sz],);
             ch[k][j]=sz++;
         }
         k=ch[k][j];
         word[k]++;
     }
 }
 void find(char *s){
     int len=strlen(s);
     int j,k=;
     for(int i=;i<len;i++){
         j=s[i]-'a';
         k=ch[k][j];
         printf("%c",s[i]);
         if(word[k]==)return;
     }
 }
 int main(){
     int x=;
     initial();
     while(~scanf("%s",s[x])){
         insert(s[x]);x++;
     }
     for(int i=;i<x;i++){
         printf("%s ",s[i]);
         find(s[i]);puts("");
     }
     return ;
 }