POJ 1094

上面的这个是自己写的

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxxn = 30;

int d[maxxn][maxxn];
int edge[maxxn][maxxn];
int e[maxxn][maxxn];
int n,m;
struct node {
	int sum;
	char id;
};

bool operator < (node x,node y) {
	return x.sum < y.sum;
	if (x.sum == y.sum) {
		return x.id < y.id;
			}
}
int floyed () {
	memcpy(e,d,sizeof(e));
	for (int k = 1;k <= n;k++) {
		for (int i = 1;i <= n;i++) {
			for (int j = 1;j <= n;j++) {
				e[i][j] |= e[i][k] & e[k][j];
				if (e[i][j] == e[j][i] && e[i][j] && i != j) return 0;
			}
		}
	}
	for (int i = 1;i <= n;i++) {
		for (int j = 1;j <= n;j++) {
			if (e[i][j] == e[j][i] && !e[i][j] && i != j) return 2;
		}
	}
	return 1;
}

int main () {
	while ((~scanf("%d %d",&n,&m)) && n && m) {
		memset(d,0,sizeof(d));
		int flag = 0;
		for (int i = 1;i <= m;i++) {
			char c[4];
			cin >> c;
			if(c[0] == c[2]) printf("Inconsistency found after %d relations.\n",i),flag = 1;
			else d[c[0] - 'A' + 1][c[2] - 'A' + 1] = 1;
			if (flag == 0) {
				int ff =  floyed();
				if (ff == 0) {
					printf ("Inconsistency found after %d relations.\n",i);
					flag = 1;
				}
				else {
					if (ff == 1) {
						printf ("Sorted sequence determined after %d relations: ",i);
						node q[maxxn];
						for (int i = 1;i <= n;i++) {
							q[i].id = i + 'A' - 1;
							q[i].sum = 0;
						}
						for (int i = 1;i <= n;i++) {
							for (int j = 1;j <= n;j++) {
								if (e[j][i]) q[i].sum++;
							}
						}
						sort(q + 1,q + 1 + n);
						for (int i = 1;i <= n;i++) {
							printf("%c",q[i].id);
						}
						cout << '.' <<endl;
						flag = 1;
					}
				}
			}	
		}
		if (flag == 0) printf("Sorted sequence cannot be determined.\n");
	}
	return 0;
}

下面的这个是标程，
基本的解释已经打了注释了

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int N = 30;
int n, m, d[N][N], e[N][N];

int floyd() {
	memcpy(e, d, sizeof(e));
	for (int k = 0; k < n; k++)
		for (int i = 0; i < n; i++)
			for (int j = 0; j < n; j++) {
				e[i][j] |= e[i][k] & e[k][j];//这里就是必须两个都是一才能是一，而且有一个是一就都是一 
				if (e[i][j] == e[j][i] && e[i][j] && i != j) return -1;//就是指如果有双向的，就是不合法的而且是矛盾 
			} 
	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++)
			if (e[i][j] == e[j][i] && !e[i][j] && i != j) return 0;//这就是指无法确定a小于b，同时无法确定b小于a 
			//之所以仍旧要写 !e[i][j]，主要是尽管上面的未触发，但是可能会出现一种现象就是尽管不会矛盾，但是可能会
			//有的未便利的点质检不连通； 
	return 1;
}

void Sorting_It_All_Out() {
	memset(d, 0, sizeof(d));
	bool flag = 1;
	for (int i = 1; i <= m; i++) {
		char s[6];
		scanf("%s", s);
		d[s[0]-'A'][s[2]-'A'] = 1;//只利用亦表示可以到达 
		if (flag) {
			int now = floyd();
			if (now == -1) {
				printf("Inconsistency found after %d relations.\n", i);//由于是直接暴力的，所以可以直接得出是那个边 
				flag = 0;
			} else if (now == 1) {
				printf("Sorted sequence determined after %d relations: ", i);
				pair<int, char> ans[N];
				for (int j = 0; j < n; j++) {
					ans[j].first = 0;
					ans[j].second = 'A' + j;//还原出原来的字符 
				}
				for (int j = 0; j < n; j++)
					for (int k = 0; k < n; k++)
						if (e[j][k]) ++ans[j].first;//从小到大遍历，并且记录其小于几个点（每小于一个点，就加一次） 
				sort(ans, ans + n);
				for (int j = n - 1; j >= 0; j--) printf("%c", ans[j].second);
				puts(".");
				flag = 0;
			}
		}
	}
	if (flag) puts("Sorted sequence cannot be determined.");//如果出现了这种情况，就是指now = 0了就是指关系不全； 
}

int main() {
	while (cin >> n >> m && n) Sorting_It_All_Out();
	return 0;
}