bzoj1574 [Usaco2009 Jan]地震损坏Damage

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=1574

【题解】

贪心把report的点的旁边所有点破坏即可。

# include <stdio.h>
# include <string.h>
# include <iostream>
# include <algorithm>
// # include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const int M = 5e5 + 10;
const int mod = 1e9+7;

# define RG register
# define ST static

int n, m, K, p[M];
bool isr[M];
int head[M], nxt[M], to[M], tot=0;

inline void add(int u, int v) {
    ++tot; nxt[tot] = head[u]; head[u] = tot; to[tot] = v;
}
inline void adde(int u, int v) {
    add(u, v), add(v, u);
}

bool vis[M];
int ans = 0;
inline void dfs(int x) {
    vis[x] = 1; ++ans;
    for (int i=head[x]; i; i=nxt[i])
        if(!vis[to[i]]) dfs(to[i]);
}

int main() {
    cin >> n >> m >> K;
    for (int i=1, u, v; i<=m; ++i) {
        scanf("%d%d", &u, &v);
        adde(u, v);
    }
    for (int i=1; i<=K; ++i) {
        scanf("%d", p+i);
        isr[p[i]] = 1;
    }
    for (int i=1, x; i<=K; ++i) {
        for (int j=head[p[i]]; j; j=nxt[j]) {
            x = to[j];
            if(!isr[x]) vis[x] = 1;
        }
    }
    dfs(1);
    cout << n-ans;
    return 0;
}