POj 1094 Sorting It All Out

这是一道标准的topsort的题目，就是判环，还有就有条件不足几种情况，只要理清了思路还是比较好些的，一开始自己不会啊，就学习了ZP同学的代码、、自己敲了两遍感觉很好啊。。向鹏哥学习啊、、、还有就是注意判重边这是一个小习惯啊、、、

Sorting It All Out

Time Limit: 1000MS Memory Limit: 10000KTotal Submissions: 24425 Accepted: 8451

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.

#include <stdio.h>#include <string.h>#include <iostream>#define N 50using namespace std;int map[N][N], list[N], du[N], re[N];int find(char * str , int n){    int start = str[0]-'A';    int end = str[2]-'A';    if(map[start][end] == 0)    {        map[start][end] = 1;        list[end] ++;    }    int i, t = 0, flat = 1, w, cnt;    for(i = 0; i < n; i++)        du[i] = list[i];    for(int k = 0; k < n; k++)    {        cnt = 0;        for(i = 0; i < n; i++)            if(du[i] == 0)            {                cnt ++;                w = i;            }        if(cnt == 0)            return -1;        else if(cnt > 1)            flat = 0;        du[w]--;        re[t++] = w;        for(i = 0; i < n; i++)            if(map[w][i] == 1)                du[i]--;    }    if(flat)        return 1;    else        return 0;}void _printf(int n, int m){    int i, j, t, flat = 1;    char str[20030];    memset(list , 0 , sizeof(list));    memset(map , 0 , sizeof(map));    for(i = 0; i < m; i++)    {        cin >>str;        if(flat)        {            t = find(str,n);            if(t == 1)            {                printf("Sorted sequence determined after %d relations: ",i+1);                for(j = 0; j < n; j++)                    printf("%c",re[j]+'A');                printf(".\n");                flat = 0;            }            else if(t == -1)            {                cout<<"Inconsistency found after "<<i+1<<" relations."<<endl;                flat = 0;            }        }    }    if(flat)        cout <<"Sorted sequence cannot be determined."<<endl;}int main(){    int n,m,i;    char str[10000];    while(cin>>n>>m)    {        if(n==0&&m==0)break;        if(n-1>m)        {            for(i=0; i<m; i++)            {                cin>>str[i];            }            cout<<"Sorted sequence cannot be determined."<<endl;        }        else        {            _printf(n,m);        }    }}