Submission #35935

#	Time	Username	Problem	Language	Result	Execution time	Memory
35935		szawinis	Chase (CEOI17_chase)	C++14	100 / 100	713 ms	334364 KiB

chase

#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
const int N = 1e5+1, V = 102;
const ll INF = 1e17;

int n, lim, a[N];
ll ans, s[N], dp[N][V][2][2]; // vertex, cnt, dir = down, up, last
vector<int> g[N];

void dfs1(int u, int p) {
	s[u] -= a[p];
	dp[u][0][0][0] = 0;
	dp[u][0][1][0] = 0;
	dp[u][1][0][1] = s[u];
	dp[u][1][1][1] = s[u];

	for(int v: g[u]) if(v != p) {
		dfs1(v, u);
		for(int x = 0; x <= lim; x++) {
			ll res[2][2] = {
				{
					max(dp[v][x][0][0], dp[v][x][0][1]),
					(x > 0 ? max(dp[v][x-1][0][0], dp[v][x-1][0][1]) + s[u] : -INF) // a[v] - a[v] cancel
				},
				{
					max(dp[v][x][1][0], dp[v][x][1][1] + a[u]),
					(x > 0 ? max(dp[v][x-1][1][0], dp[v][x-1][1][1] + a[u]) + s[u] - a[v] : -INF)
				}
			};
			for(int i = 0; i < 2; i++) for(int j = 0; j < 2; j++) {
				dp[u][x][i][j] = max(res[i][j], dp[u][x][i][j]);
				if(dp[u][x][i][j] < 0) dp[u][x][i][j] = -INF;
				// cout << u << ' ' << x << ' ' << i << ' ' << j << ' ' << dp[u][x][i][j] << endl;
			}
		}
	}
}

void dfs2(int u, int p) {
	for(int x = 0; x <= lim; x++)
		for(int i = 0; i < 2; i++)
			for(int j = 0; j < 2; j++) ans = max(dp[u][x][i][j] + bool(j) * a[p], ans);

	for(int v: g[u]) if(v != p) dfs2(v, u);
	vector<ll> mx(lim+1);
	for(int v: g[u]) if(v != p) {
		for(int x = 0; x <= lim; x++) {
			ll res = max(dp[v][x][1][0], dp[v][x][1][1] + a[u]);
			res += max((x < lim ? mx[lim-x-1] + s[u] - a[v] + a[p] : 0), mx[lim-x]);
			ans = max(res, ans);
			// cout << u << ' ' << v << ' ' << x << ' ' << res << endl;
		}

		for(int x = 0; x <= lim; x++) {
			mx[x] = max(max(dp[v][x][0][0], dp[v][x][0][1]), mx[x]);
			mx[x] = max((x > 0 ? mx[x-1] : 0), mx[x]);
		}
	}
	reverse(g[u].begin(), g[u].end());
	mx.clear();
	mx.resize(lim+1);
	for(int v: g[u]) if(v != p) {
		for(int x = 0; x <= lim; x++) {
			ll res = max(dp[v][x][1][0], dp[v][x][1][1] + a[u]);
			res += max((x < lim ? mx[lim-x-1] + s[u] - a[v] + a[p] : 0), mx[lim-x]);
			ans = max(res, ans);
			// cout << u << ' ' << v << ' ' << x << ' ' << res << endl;
		}

		for(int x = 0; x <= lim; x++) {
			mx[x] = max(max(dp[v][x][0][0], dp[v][x][0][1]), mx[x]);
			mx[x] = max((x > 0 ? mx[x-1] : 0), mx[x]);
		}
	}
}

int main() {
	scanf("%d %d", &n, &lim);
	for(int i = 1; i <= n; i++) scanf("%d", a+i);
	for(int i = 1, u, v; i < n; i++) {
		scanf("%d %d", &u, &v);
		g[u].push_back(v);
		g[v].push_back(u);
		s[u] += a[v];
		s[v] += a[u];
	}
	for(int v = 0; v <= n; v++)
		for(int x = 0; x <= lim; x++)
			for(int i = 0; i < 2; i++) for(int j = 0; j < 2; j++) dp[v][x][i][j] = -INF;

	dfs1(1, 0);
	dfs2(1, 0);
	// for(int x = 0; x <= lim; x++) for(int i = 0; i < 2; i++) for(int j = 0; j < 2; j++) ans = max(dp[1][x][i][j], ans);
	printf("%lld", ans);
}

Compilation message (stderr)

chase.cpp: In function 'int main()':
chase.cpp:82:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &lim);
                          ^
chase.cpp:83:46: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i = 1; i <= n; i++) scanf("%d", a+i);
                                              ^
chase.cpp:85:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
                         ^

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