POJ2001 (Shortest Prefixes）
Shortest Prefixes
| Time Limit: 1000MS | Memory Limit: 30000K | |
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".
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
Source
第一道trie。。题目求的是每个字符串的的前缀且这个前缀不是其他字符串的前缀。
1 #include<set> 2 #include<map> 3 #include<queue> 4 #include<cstdio> 5 #include<cstdlib> 6 #include<cstring> 7 #include<iostream> 8 #include<algorithm> 9 using namespace std; 10 const int N = 30; 11 const int MAXN = 1010; 12 #define For(i,n) for(int i=1;i<=n;i++) 13 #define Rep(i,l,r) for(int i=l;i<=r;i++) 14 15 char word[MAXN][N],ans[N]; 16 int n; 17 18 struct trie{ 19 int sz,ch[MAXN*N][N],v[MAXN*N]; 20 trie(){sz=1;} 21 void insert(char st[]){ 22 int len=strlen(st);int now=1;v[now]++; 23 Rep(i,0,len-1){ 24 int id=st[i]-'a'; 25 if(!ch[now][id]) ch[now][id]=++sz; 26 v[now=ch[now][id]]++; 27 } 28 } 29 void prefix(char st[],char *ans){ 30 int now=1,len=strlen(st); 31 Rep(i,0,len-1){ 32 int id=st[i]-'a'; 33 if(v[now]==1){ans[i]='\0';return;} 34 ans[i]=st[i]; 35 now=ch[now][id]; 36 } 37 ans[len]='\0'; 38 } 39 }trie; 40 41 int main(){ 42 #ifndef ONLINE_JUDGE 43 freopen("prefix.in","r",stdin); 44 #endif 45 for(n=1;scanf("%s",word[n])!=EOF;n++) trie.insert(word[n]); 46 For(i,n) { 47 trie.prefix(word[i],ans); 48 printf("%s %s\n",word[i],ans); 49 } 50 return 0; 51 }
