Sorting It All Out

Sorting It All Out

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 6
A<B
A<C
B<C
C<D
B<D
A<B
3 2
A<B
B<A
26 1
A<Z
0 0

Sample Output

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

这个题我感觉唯一比较坑的就是它可以在没有输入全部一组数据的时候就可以输出，第一次写这个题的时候把我坑惨了，然后就是你每输入一条数据就用拓扑查一次。
代码：

#include<stdio.h>
#include<string.h>
int f[30][30],t[30],b[30],d[30],sum,n,m;
char r[30];
int tp()
{
    int flag=0,l=0;
    for(int v=1; v<=sum; v++)
    {
        int k=-1,num=0;
        for(int i=0; i<n; i++)
        {
            if(d[i]&&!t[i])
            {
                k=i;
                num++;
            }
        }
        if(k==-1)
            return -1;
        if(num!=1)
            flag=1;
        t[k]=-1;
        r[l]='A'+k;
        l++;
        for(int i=0; i<n; i++)
        {
            if(f[k][i])
                t[i]--;
        }
    }
    r[l]=0;
    if(sum==n&&flag==0)
        return 1;
    return 0;
}
int main()
{
    while(~scanf("%d%d",&n,&m),n||m)
    {
        sum=0;
        memset(f,0,sizeof(f));
        memset(b,0,sizeof(b));
        memset(t,0,sizeof(t));
        memset(d,0,sizeof(d));
        int flag=0;
        for(int i=1; i<=m; i++)
        {
            char s[3];
            scanf("%s",s);
            if(flag)
                continue;
            int x=s[0]-'A',y=s[2]-'A';
            if(!d[x])
            {
                sum++;
                d[x]=1;
            }
            if(!d[y])
            {
                sum++;
                d[y]=1;
            }
            if(!f[x][y])
            {
                f[x][y]=1;
                b[y]++;
                for(int j=0; j<26; j++)
                    t[j]=b[j];
                int a=tp();
                if(a==-1)
                {
                    printf("Inconsistency found after %d relations.\n",i);
                    flag=1;
                }
                if(a==1)
                {
                    printf("Sorted sequence determined after %d relations: %s.\n",i,r);
                    flag=1;
                }
            }
        }
        if(!flag)
            printf("Sorted sequence cannot be determined.\n");
    }
}

标签：Sorting,sequence,30,relations,determined,Sorted,sorted,Out
来源： https://blog.csdn.net/Yyxiaobb/article/details/97617792