Sorting It All Out POJ（拓扑排序+floyd）

一个就是简单的拓扑排序，一个就是利用floyd判断是否存在环

#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
#define MAXD 30
#define MAX_SIZE 1000
vector<int>G[MAXD];
int n,m;
char L[MAXD];
int du[MAXD];
int maps[MAXD][MAXD];
int Floyd(){
    for(int k = 0; k < n; k++)
        for(int i = 0; i < n ; i++)
         for(int j = 0; j < n;  j++)
           if(maps[i][k] && maps[k][j])
             maps[i][j] = 1;
    for(int i = 0; i < n ; i++)
        if(maps[i][i]) return 0;
    return 1;
}
int toposort(){
    memset(du,0,sizeof(du));
    for(int i = 0; i < n ; i++)
        for(int j = 0; j < G[i].size(); j++){
        du[G[i][j]] ++;
        //printf("%d %d\n",i,j);
    }
    queue<int>q;
    int cnt = 0;
    for(int i = 0;i < n ;i++)
        if(!du[i]) q.push(i);
    while(!q.empty()){
        if(q.size() > 1) return 0;
        int t = q.front(); q.pop();
        L[cnt ++] = t + 'A';
        //printf("%c\n",t + 'A');
        for(int i = 0 ; i < G[t].size(); i++){
            int x = G[t][i];
            du[x]--;
            if(!du[x])
                q.push(x);
        }
    }
    if(cnt == n) return 1;
    else         return -1;
}
int main(){
    while(scanf("%d%d",&n,&m)){
        if(!n && !m) break;
        for(int i = 0; i < n ; i++)
            G[i].clear();
        int i;
        memset(maps,0,sizeof(maps));
        char a[MAX_SIZE],b[MAX_SIZE],c[MAX_SIZE];
        for(int i = 0; i < m ; i++){
            getchar();
            scanf("%c%c%c",&a[i],&b[i],&c[i]);
        }
        for(i = 0; i < m ; i++){
            char x,y,z;
            int flag;
            x = a[i]; y = c[i]; z = b[i];
            maps[x - 'A'][y - 'A'] = 1;
            flag = Floyd();
            if(flag == 0){
                printf("Inconsistency found after %d relations.\n",i + 1);
                break;
            }
            if(z == '<')
            G[x - 'A'].push_back(y - 'A');
            else
            G[y - 'A'].push_back(x - 'A');
            if(toposort() == 1){
                L[n] = '\0';
                printf("Sorted sequence determined after %d relations: %s.\n",i + 1,L);
                break;
            }
            else if(toposort() == -1){
                printf("Inconsistency found after %d relations.\n",i + 1);
                break;
            }
        }
        if(i == m)
            printf("Sorted sequence cannot be determined.\n");
    }
    return 0;
}