Submission #848547

#	Time	Username	Problem	Language	Result	Execution time	Memory
848547		qthang2k11	Chase (CEOI17_chase)	C++17	20 / 100	207 ms	524288 KiB

chase

#include <bits/stdc++.h>
using namespace std;
 
using ll = long long;
 
const int N = 1e5 + 5;
 
template<class X, class Y>
inline void maxi(X &x, Y y) {
	if (x < y) x = y;
}
 
vector<int> g[N];
int n, k, a[N];
ll s[N];
 
ll ans = 0;
 
struct Node {
	ll val[101][2];
	
	Node() { 
		memset(val, -63, sizeof val); 
	}
	
	void maxi_(const Node &other) {
		for (int i = 0; i <= k; i++)
			for (int j = 0; j < 2; j++)
				maxi(val[i][j], other.val[i][j]);
	}
	
	void deal(const Node &other, const int &x, const int &y) { // update from y to x
		for (int i = 0; i <= k; i++) {
			for (int j = 0; j < 2; j++) {
				ll cur = other.val[i][j];
				if (i < k) {
					if (j) maxi(val[i + 1][1], cur + s[x] - a[y]);
					else maxi(val[i + 1][1], cur + s[x] - a[y]);
				}
				maxi(val[i][0], cur);
			}
		}
	}
	
	Node deal_(const int &x, const int &y) { // update from y to x
		Node ans;
		for (int i = 0; i <= k; i++) {
			for (int j = 0; j < 2; j++) {
				ll cur = val[i][j];
				if (i < k) {
					if (j) maxi(ans.val[i + 1][1], cur + s[x] - a[y]);
					else maxi(ans.val[i + 1][1], cur + s[x] - a[y]);
				}
				maxi(ans.val[i][0], cur);
			}
		}
		return ans;
	}
	
	ll res() const {
		ll ans = 0;
		for (int i = 0; i <= k; i++)
			for (int j = 0; j < 2; j++)
				maxi(ans, val[i][j]);
		return ans;
	}
 
};

Node dp[N], pref[N], suf[N];
 
void dfs_init(int x, int p) {
	for (int i = g[x].size() - 1; i >= 0; i--) {
		int y = g[x][i];
		if (y != p) continue;
		swap(g[x].back(), g[x][i]);
		g[x].pop_back();
	}
	for (int y: g[x]) 
		dfs_init(y, x);
}
 
void dfs(int x) {
	for (int y: g[x]) {
		dfs(y);
		dp[x].deal(dp[y], x, y);
	}
	maxi(dp[x].val[0][0], 0);
	if (k > 0) maxi(dp[x].val[1][1], s[x]);
	maxi(ans, dp[x].res());
}
 
void dfs_reroot(int x, Node down) {
	maxi(down.val[0][0], 0);
	if (k > 0) maxi(down.val[1][1], s[x]);
	maxi(ans, down.res());
	suf[(int)g[x].size()] = pref[0] = Node();
	for (int i = 0, o = g[x].size(); i < o; i++) {
		int y = g[x][i];
		auto &p = pref[i];
		if (i) p.maxi_(pref[i - 1]);
		p.deal(dp[y], x, y);
	}
	for (int o = g[x].size(), i = o - 1; i >= 0; i--) {
		int y = g[x][i];
		auto &p = suf[i];
		p = suf[i + 1];
		p.deal(dp[y], x, y);
	}
	for (int i = 0, o = g[x].size(); i < o; i++) {
		int y = g[x][i];
		Node cur = down;
		if (i > 0) cur.maxi_(pref[i - 1]);
		if (i + 1 < o) cur.maxi_(suf[i + 1]);
		dfs_reroot(y, cur.deal_(y, x));
	}
}
 
int32_t main() {
	cin.tie(0)->sync_with_stdio(0);
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	for (int i = 1; i < n; i++) {
		int x, y;
		cin >> x >> y;
		g[x].emplace_back(y);
		g[y].emplace_back(x);
	}
	for (int x = 1; x <= n; x++) {
		for (int y: g[x])
			s[x] += a[y];
	}
	dfs_init(1, 0);
	dfs(1);
	dfs_reroot(1, Node());
	cout << ans;
	return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 0 / 20
• Subtask 3: 0 / 30
• Subtask 4: 0 / 30