29 August

P1352 Bosses' Masquerade

树形DP模板。

#include <cstdio>
#include <algorithm>
using namespace std;

int n, r[6003], f[6003][2], v[6003], root, ans;
int head[6003], nex[6003], to[6003];

inline void add(int x, int y) {
	nex[++head[0]]=head[x], head[x]=head[0], to[head[0]]=y;
}

void dp(int x) {
	f[x][1]=r[x];
	for (register int k=head[x]; k; k=nex[k]) 
		dp(to[k]),
		f[x][0]+=max(f[to[k]][0], f[to[k]][1]),
		f[x][1]+=f[to[k]][0];
}

int main() {
	scanf("%d", &n);
	for (register int i=1; i<=n; ++i) scanf("%d", &r[i]);
	for (register int i=1, l, k; i<n; ++i)
		scanf("%d%d", &l, &k), add(k, l), v[l]=1;
	for (register int i=1; i<=n; ++i) if (!v[i]) {root=i; break; }
	dp(root);
	printf("%d\n", max(f[root][0], f[root][1]));
	return 0;
}