COJ 1081 集训队分组

http://acm.csu.edu.cn/OnlineJudge/problem.php?id=1081

不是太会写拓扑排序，所以再写一遍。

/*Accepted    880 kb    268 ms    C++/    1671 B    2012-07-29 17:08:30*/
#include<cstdio>
#include<cstring>
#include<cstdlib>const int MAXN = 1 << 10;
const int MAXM = 10010;int N, K, M, first[MAXN], e, next[MAXM], v[MAXM];
int topo[MAXN], cnt, vis[MAXN];void addedge(int x, int y)
{v[e] = y;next[e] = first[x], first[x] = e ++;
}void ReadGraph()
{int i, x, y;memset(first, -1, sizeof first);e = 0;for(i = 0; i < M; i ++){scanf("%d%d", &x, &y);addedge(x, y);}
}void dfs(int cur)
{int i;vis[cur] = 1;for(i = first[cur]; i != -1; i = next[i])if(!vis[v[i]])dfs(v[i]);topo[cnt --] = cur;
}void toposort()
{int i;cnt = N;memset(vis, 0, sizeof vis);for(i = 1; i <= N; i ++)if(!vis[i])dfs(i);
}void Search(int cur)
{int i;vis[cur] = 1;for(i = first[cur]; i != -1; i = next[i])if(!vis[v[i]])Search(v[i]);
}bool judge()
{int i, j;for(i = 1; i <= K; i ++){memset(vis, 0, sizeof vis);Search(topo[i]);for(j = K + 1; j <= N; j ++)if(!vis[topo[j]])return false;}return true;
}int main()
{while(scanf("%d%d%d", &N, &K, &M) == 3){ReadGraph();toposort();bool ok = judge();if(ok)printf("YES\n");elseprintf("NO\n");}return 0;
}