叶子的颜色---经典树上dp

挺简单的一个dp

 

 

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#define maxn 10100
using namespace std;
const int INF = 0x3f3f3f3f;
vector<int>G[maxn];
void insert(int be, int en) {
	G[be].push_back(en);
}
int n, m;
int h[maxn];
int b[maxn];
int vis[maxn];

int dfs(int x, int fa) {
	h[x] = 1;
	b[x] = 1;
	if (vis[x] == 0) {
		b[x] = INF;
	}
	if (vis[x] == 1) {
		h[x] = INF;
	}
	for (int i = 0; i < G[x].size(); i++) {
		int p = G[x][i];
		if (p == fa) continue;
		dfs(p, x);
		h[x] += min(b[p], h[p] - 1);	
		b[x] += min(h[p], b[p] - 1);
	}
	return 0;
}

int main() {
	memset(vis, -1, sizeof(vis));
	scanf("%d %d", &n, &m);
	
	int op;
	for (int i = 1; i <= m; i++) {
		scanf("%d", &op);
		vis[i] = op;
	}
	int be, en;
	int root = n;
	for (int i = 1; i < n; i++) {
		scanf("%d %d", &be, &en);
		insert(be, en);
		insert(en, be);
	}
	dfs(n, -1);
	printf("%d\n", min(h[n], b[n]));
	return 0;
}