Compound Words

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本文介绍了一种算法，用于判断一组二进制编码是否具备即时可解码特性，即任一符号的编码都不是其他符号编码的前缀。通过构建特定的数据结构，该算法能有效地检查给定的编码集合是否满足条件，并提供了完整的实现代码。

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A - Immediate Decodability

Crawling in process...Crawling failedTime Limit:3000MS Memory Limit:0KB 64bit IO Format:%lld & %llu

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Description

Immediate Decodability

An encoding of a set of symbols is said to be immediately decodable if no code for one symbol is the prefix of a code for another symbol. We will assume for this problem that all codes are in binary, that no two codes within a set of codes are the same, that each code has at least one bit and no more than ten bits, and that each set has at least two codes and no more than eight.

Examples: Assume an alphabet that has symbols {A, B, C, D}

The following code is immediately decodable:

A:01 B:10 C:0010 D:0000

but this one is not:

A:01 B:10 C:010 D:0000 (Note that A is a prefix of C)

Input

Write a program that accepts as input a series of groups of records from a data file. Each record in a group contains a collection of zeroes and ones representing a binary code for a different symbol. Each group is followed by a single separator record containing a single 9; the separator records are not part of the group. Each group is independent of other groups; the codes in one group are not related to codes in any other group (that is, each group is to be processed independently).

Output

For each group, your program should determine whether the codes in that group are immediately decodable, and should print a single output line giving the group number and stating whether the group is, or is not, immediately decodable.

The Sample Input describes the examples above.

Sample Input

Sample Output

Set 1 is immediately decodable
Set 2 is not immediately decodable

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<malloc.h>
int tb = 0;
struct node
{
    int flag;
    struct node *next[10];
} ab[100000];
struct node1
{
    char str1[15];
} NODE[21000];
struct node *creat()
{
    int i;
    struct node *p;
    p=&ab[tb++];
    for(i=0; i<10; i++)
    {
        p->next[i]=NULL;
    }
    p->flag=0;
    return p;
}
int cmp(const void *a, const void *b)
{
    struct node1 *p1 = (struct node1 *)a;
    struct node1 *p2 = (struct node1 *)b;
    if(strcmp((*p1).str1,(*p2).str1)>0)
    {
        return 1;
    }
    else if(strcmp((*p1).str1,(*p2).str1)==0)
    {
        return 0;
    }
    else
    {
        return -1;
    }
}
int Insert(struct node *p,char *s)
{
    int i,n,num;
    n=strlen(s);
    for(i=0; i<n; i++)
    {
        if(s[i]>='0'&&s[i]<='9') num=s[i]-'0';
        if(p->next[num]==NULL)
        {
            p->next[num]=creat();
        }
        p=p->next[num];
        if(p->flag) return 1;
    }
    p->flag=1;
    return 0;
}
int main()
{
    int i,j,n,m;
    struct node *p;
    int k=1;
    while(~scanf("%s",NODE[0].str1))
    {
        tb = 0;
        p=creat();
        for(i=1; ;i++)
        {
            scanf("%s",NODE[i].str1);
            if(strcmp(NODE[i].str1,"9")==0) break;

        }
        qsort(NODE,i,sizeof(NODE[0]),cmp);
        int s=0;
        for(j=0; j<i; j++)
        {
            s=Insert(p,NODE[j].str1);
            if(s) break;
        }
        if(s) printf("Set %d is not immediately decodable\n",k);
        else printf("Set %d is immediately decodable\n",k);
        k++;
    }
    return 0;
}