POJ 1094 Sorting It All Out ——拓扑排序（有点坑）

Sorting It All Out

Time Limit: 1000MS
Memory Limit: 10000KTotal Submissions: 28628
Accepted: 9896

Description

An ascending sorted sequence of distinct values is one in which some form of a less-than operator is used to order the elements from smallest to largest. For example, the sorted sequence A, B, C, D implies that A < B, B < C and C < D. in this problem, we will give you a set of relations of the form A < B and ask you to determine whether a sorted order has been specified or not.

Input

Input consists of multiple problem instances. Each instance starts with a line containing two positive integers n and m. the first value indicated the number of objects to sort, where 2 <= n <= 26. The objects to be sorted will be the first n characters of the uppercase alphabet. The second value m indicates the number of relations of the form A < B which will be given in this problem instance. Next will be m lines, each containing one such relation consisting of three characters: an uppercase letter, the character "<" and a second uppercase letter. No letter will be outside the range of the first n letters of the alphabet. Values of n = m = 0 indicate end of input.

Output

For each problem instance, output consists of one line. This line should be one of the following three: 

Sorted sequence determined after xxx relations: yyy...y. 
Sorted sequence cannot be determined. 
Inconsistency found after xxx relations. 

where xxx is the number of relations processed at the time either a sorted sequence is determined or an inconsistency is found, whichever comes first, and yyy...y is the sorted, ascending sequence. 

Sample Input

4 6A<BA<CB<CC<DB<DA<B3 2A<BB<A26 1A<Z0 0

Sample Output

Sorted sequence determined after 4 relations: ABCD.Inconsistency found after 2 relations.Sorted sequence cannot be determined.

Source

East Central North America 2001

错了好几遍不知道自己怎么错的，看了看讨论，才知道需要每输入一组数据就要排序一次，只能说真坑。。。。。

#include <stdio.h>#include <string.h>bool mp[27][27];int deg[27];int s[27];int num;int toposort(int n){    int tmp[27],flag = 2;    memset(s,0,sizeof(s));    for(int i = 1;i <= n;i++)        tmp[i] = deg[i];    for(int i = 1;i <= n;i++)    {        int js = 0,bj = 0;        for(int j = 1;j <= n;j++)        {            if(!tmp[j])            {                js++;                bj = j;            }        }        if(!js)            return 0;//有环        if(js > 1)            flag = 1;//有待于进一步排序        s[i] = bj;        tmp[bj] = -1;        for(int j = 1;j <= n;j++)        {            if(mp[bj][j])            {                tmp[j]--;            }        }    }    return flag;}int main(){    int n,m,bj,fh;    char sr[10];    while(scanf("%d%d",&n,&m),n || m)    {        num = 0;        bool flag = true;        memset(mp,false,sizeof(mp));        memset(deg,0,sizeof(deg));        for(int i = 0;i < m;i++)        {            scanf("%s",sr);            if(!flag)                continue;            int zh1 = sr[0] - 'A' + 1;            int zh2 = sr[2] - 'A' + 1;            if(!mp[zh1][zh2])            {                mp[zh1][zh2] = true;                deg[zh2]++;            }            fh = toposort(n);            if(fh == 0 || fh == 2)            {                bj = i + 1;                flag = false;            }        }        if(fh == 0)        {            printf("Inconsistency found after %d relations.\n",bj);        }        else if(fh == 2)        {            printf("Sorted sequence determined after %d relations: ",bj);            for(int i = 1;i <= n;i++)                printf("%c",char(s[i] + 'A' - 1));            printf(".\n");        }        else if(fh == 1 && flag)        {            printf("Sorted sequence cannot be determined.\n");        }    }    return 0;}