【Codevs1380】没有上司的舞会【树上最大独立集】【TreeDP】

【题目链接】

复习一下TreeDP。

1A。

/* Pigonometry */
#include <cstdio>
#include <algorithm>

using namespace std;

const int maxn = 6005;

int n, dp[maxn][2], w[maxn], head[maxn], cnt;

struct _edge {
	int v, next;
} g[maxn << 1];

inline int iread() {
	int f = 1, x = 0; char ch = getchar();
	for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;
	for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
	return f * x;
}

inline void add(int u, int v) {
	g[cnt] = (_edge){v, head[u]};
	head[u] = cnt++;
}

inline void dfs(int x, int f) {
	dp[x][1] = w[x];
	for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ f) {
		dfs(g[i].v, x);
		dp[x][0] += max(dp[g[i].v][0], dp[g[i].v][1]);
		dp[x][1] += dp[g[i].v][0];
	}
}

int main() {
	n = iread();
	for(int i = 1; i <= n; i++) w[i] = iread(), head[i] = -1; cnt = 0;
	for(int i = 1; i < n; i++) {
		int u = iread(), v = iread();
		add(u, v); add(v, u);
	}

	dfs(1, 0);

	printf("%d\n", max(dp[1][0], dp[1][1]));
	return 0;
}