【Codevs1380】没有上司的舞会【树上最大独立集】【TreeDP】

/* 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;
}