【BZOJ2103】【BZOJ2447】Fire 消防站【DFS】【TreeDP】

【题目链接】 【题目链接】

同【BZOJ3302题解】

/* Pigonometry */
#include 
#include 

using namespace std;

typedef long long LL;

const int maxn = 50005, inf = 0x3f3f3f3f;

int n, head[maxn], cnt, pre[maxn], depth[maxn], son[maxn], bro[maxn];
LL sum[maxn], res[maxn], ans;

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) {
	for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x]) {
		depth[g[i].v] = depth[x] + 1;
		pre[g[i].v] = x;
		dfs(g[i].v);
		sum[x] += sum[g[i].v];
		res[x] += res[g[i].v] + sum[g[i].v];
		if(!son[x] || sum[g[i].v] > sum[son[x]]) bro[x] = son[x], son[x] = g[i].v;
		else if(!bro[x] || sum[g[i].v] > sum[bro[x]]) bro[x] = g[i].v;
	}
}

int cut;

inline void center(LL &ret, int root, int x, LL k) {
	ret = min(ret, k);
	int v = son[x];
	if(v == cut || sum[bro[x]] > sum[son[x]]) v = bro[x];
	if(!v) return;
	center(ret, root, v, k + sum[root] - 2 * sum[v]);
}

inline void solve(int x) {
	for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x]) {
		cut = g[i].v;
		LL gx = inf, gy = inf;
		for(int j = x; j; j = pre[j]) sum[j] -= sum[cut];
		center(gx, 1, 1, res[1] - res[cut] - depth[cut] * sum[cut]);
		center(gy, cut, cut, res[cut]);
		ans = min(ans, gx + gy);
		for(int j = x; j; j = pre[j]) sum[j] += sum[cut];
		solve(g[i].v);
	}
}

int main() {
	n = iread();
	for(int i = 1; i <= n; i++) head[i] = -1; cnt = 0;

	for(int i = 1; i < n; i++) {
		int u = iread(), v = iread();
		add(u, v); add(v, u);
	}
	for(int i = 1; i <= n; i++) sum[i] = iread();

	ans = inf;
	dfs(1);
	solve(1);
	printf("%lld\n", ans);
	return 0;
}