Submission #1271211

#	Time	Username	Problem	Language	Result	Execution time	Memory
1271211		goulthen	Cat Exercise (JOI23_ho_t4)	C++20	100 / 100	285 ms	80276 KiB

Main

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define ll long long
#define rep(i,a,b) for (int i = a; i <= b; i++)
#define per(i,a,b) for (int i = a; i >= b; i--)
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back

const int MAXN = 2e5+10;
const int INF = 1e18 + 5;
vector<int> g[MAXN];
int a[MAXN],rp[MAXN],sz[MAXN], mx[MAXN], inv[MAXN], val[MAXN], dep[MAXN], anc[MAXN][31];

int find(int x) {
	if (rp[x] == x) return x;
	return rp[x] = find(rp[x]);
}

void join(int x, int y) {
	x = find(x), y = find(y);

	if (x==y)return;
	if (sz[x] > sz[y]) swap(x,y);

	rp[x] = y;
	if(a[mx[y]] < a[mx[x]]) mx[y] = mx[x];
	sz[y] += sz[x];
}

void dfs(int u, int p = 1) {
	anc[u][0] = p;
	for (int &v : g[u]) {
		if (v==p) continue;
		dep[v] = dep[u] + 1;

		dfs(v,u);
	}
}

int getu(int u, int jmp) {
	int ans = u, cur = 0;

	while (jmp > 0) {
		if (jmp&1) ans = anc[ans][cur];
		cur++;
		jmp/=2;
	}

	return ans;
}

int dist(int u, int v) {
	if (dep[u] < dep[v]) swap(u,v);
	int lu = u, lv = v;
	lu = getu(lu,dep[u]-dep[v]);

	per(k,30,0) {
		if (anc[lu][k] != anc[lv][k]) {
			lu = anc[lu][k];
			lv = anc[lv][k];
		}
	}
	if(lu!=lv) lu = anc[lu][0];

	return dep[u] + dep[v] - 2*dep[lu];
}

int32_t main() {
	ios_base::sync_with_stdio(0); cin.tie(nullptr);
	int n; cin >> n;
	rep(i,1,n) {
		cin >> a[i];
		inv[a[i]] = i;
	}
	rep(i,1,n) rp[i] = i, sz[i] = 1, mx[i] = i;
	rep(i,1,n-1) {
		int u,v;cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
	}

	dfs(1);

	rep(k,1,30) {
		rep(i,1,n) {
			anc[i][k] = anc[anc[i][k-1]][k-1];
		}
	}

	rep(i,1,n) {
		int x = inv[i];
		for (int &v : g[x]) {
			if (a[v] > i) continue;
			val[x] = max(val[x], dist(x,mx[find(v)]) + val[mx[find(v)]]);
			join(x,v);
		}
	}

	cout << val[inv[n]] << '\n';

	return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26