「Bzoj 1648」「Usaco2006 Dec」Cow Picnic 奶牛野餐 (DFS)

BZOJ 1648
Luogu 2853
from: USACO 2006 Dec Sliver(USACO刷题第8题)

记录一下每个牧场的奶牛个数，之后如果一个牧场有牛就dfs遍历，把遍历到的点的$tot[i]$都加上这个奶牛数，然后最后统计每个牧场如果$tot[i]=k$那么就是一个答案。

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<stack>
#include<vector>
#define ms(i, j) memset(i, j, sizeof i)
#define LL long long
using namespace std;

const int MAXN = 1000 + 5;

vector<int> G[MAXN];
int cs[MAXN], vi[MAXN], tot[MAXN], k, n, m;

void dfs(int u, int s) {
    tot[u] += s;
    for (int i=0;i<G[u].size();i++) {
        int v = G[u][i];
        if (!vi[v]) {
            vi[v] = true;
            dfs(v, s);
        }
    }
}
void clear() {
    ms(tot, 0);
    ms(cs, 0);
}
void init() {
    clear();
    for (int i=1;i<=k;i++) {
        int ki;
        scanf("%d", &ki);
        cs[ki]++;
    }
    for (int i=1;i<=m;i++) {
        int a, b;
        scanf("%d%d", &a, &b);
        G[a].push_back(b);
    }
}
void solve() {
    for (int i=1;i<=n;i++) {
        if (cs[i]) {
            ms(vi, 0), vi[i] = true;
            dfs(i, cs[i]);
        }
    }
    int ans = 0;
    for (int i=1;i<=n;i++) if (tot[i]==k) ans++;
    printf("%d\n", ans);
}
int main() {
    #ifndef ONLINE_JUDGE
    freopen("1.in", "r", stdin);freopen("1.out", "w", stdout);
    #endif
    while (scanf("%d%d%d", &k, &n, &m)==3&&k&&n&&m) init(), solve();
    return 0;
}