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Submission #676702

# Submission time Handle Problem Language Result Execution time Memory
676702 2022-12-31T18:09:07 Z QwertyPi Islands (IOI08_islands) C++14
80 / 100
 615 ms 131072 KB 
#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
 
const int N = 1e6 + 11;
 
// 16
vector<vector<pair<int, int>>> G(N);
 
// 32
int p[N], w[N], tin[N], t = 0;
long long dp[N];
bool vis[N], cyc[N];
 
// 12
struct edge{
	int u, v, w;
};
vector<edge> extra;
 
void dfs(int id, int v, int pa = -1){
	vis[v] = true; tin[v] = ++t;
	for(auto i : G[v]){
		if(!vis[i.fi]){
			p[i.fi] = v;
			dfs(id, i.fi, v);
			w[i.fi] = i.se;
		}else if(i.fi != pa){
			extra[id] = {v, i.fi, i.se};
		}
	}
}
 
bool is_anc(int u, int v){
	return tin[u] <= tin[v];
}
 
long long dfs_dp(int id, int v, int pa = -1){
	long long mx1 = 0, mx2 = 0;
	long long ans = 0;
	for(auto i : G[v]){
		if(!cyc[i.fi] && i.fi != pa){
			long long r = dfs_dp(id, i.fi, v);
			ans = max(ans, r);
			long long v = dp[i.fi] + i.se;
			if(v > mx1) mx2 = mx1, mx1 = v;
			else if(v > mx2) mx2 = v;
		}
	}
	ans = max(ans, mx1 + mx2); dp[v] = mx1;
	return ans;
}
 
long long solve(int id, vector<long long>& DP, vector<long long>& W){
	int n = W.size();
	for(int i = 0; i < n; i++){
		W.push_back(W[i]);
	}
	W.push_back(0);
	for(int i = (int) W.size() - 2; i >= 0; i--){
		W[i] = W[i + 1] - W[i];
	}
	// 4
	deque<int> v;
	for(int i = 0; i < n; i++){
		while(v.size() && DP[i] + W[i] >= DP[v.back()] + W[v.back()]) v.pop_back();
		v.push_back(i);
	}
	long long ans = 0;
	for(int i = 0; i < n; i++){
		if(v.front() == i) v.pop_front();
		ans = max(ans, DP[i] - W[i] + DP[v.front() % n] + W[v.front()]);
		while(v.size() && DP[i] + W[i + n] >= DP[v.back() % n] + W[v.back()]) v.pop_back();
		v.push_back(i + n);
	}
	return ans;
}
 
int32_t main(){
	cin.tie(0); cout.tie(0)->sync_with_stdio(false);
	int n; cin >> n;
	for(int i = 1; i <= n; i++){
		int v, _w; cin >> v >> _w;
		G[i].push_back({v, _w});
		G[v].push_back({i, _w});
	}
	for(int i = 1; i <= n; i++){
		G[i].shrink_to_fit();
	}
	
	for(int i = 1; i <= n; i++){
		if(!vis[i]){
			extra.resize(extra.size() + 1);
			dfs(extra.size() - 1, i);
		}
	}
	
	// 20
	int CC = extra.size();
	long long ans = 0;
	for(int i = 0; i < CC; i++){
		vector<int> cyc_L, cyc_R;
		int x = extra[i].u, y = extra[i].v;
		while(!is_anc(x, y)){
			cyc[x] = true;
			cyc_L.push_back(x);
			x = p[x];
		}
		while(!is_anc(y, x)){
			cyc[y] = true;
			cyc_R.push_back(y);
			y = p[y];
		}
		int l = x;
		cyc[l] = true;
		long long rans = 0;
		for(auto v : cyc_L){
			rans = max(rans, dfs_dp(i, v));
		}
		for(auto v : cyc_R){
			rans = max(rans, dfs_dp(i, v));
		}
		rans = max(rans, dfs_dp(i, l));
		vector<long long> W, DP;
		for(auto i : cyc_L){
			DP.push_back(dp[i]);
			W.push_back(w[i]);
		}
		DP.push_back(dp[l]);
		for(int i = (int) cyc_R.size() - 1; i >= 0; i--){
			DP.push_back(dp[cyc_R[i]]);
			W.push_back(w[cyc_R[i]]); 
		}
		cyc_L.resize(0); cyc_R.resize(0);
		W.push_back(extra[i].w);
		rans = max(rans, solve(i, DP, W));
		ans += rans;
	}
	cout << ans << endl;
}

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 23764 KB Output is correct
2 Correct 12 ms 23764 KB Output is correct
3 Correct 13 ms 23892 KB Output is correct
4 Correct 13 ms 23764 KB Output is correct
5 Correct 12 ms 23764 KB Output is correct
6 Correct 12 ms 23764 KB Output is correct
7 Correct 12 ms 23792 KB Output is correct
8 Correct 11 ms 23764 KB Output is correct
9 Correct 12 ms 23764 KB Output is correct
10 Correct 12 ms 23764 KB Output is correct
11 Correct 14 ms 23852 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 23892 KB Output is correct
2 Correct 12 ms 23892 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 13 ms 23996 KB Output is correct
2 Correct 17 ms 24276 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 24992 KB Output is correct
2 Correct 27 ms 27836 KB Output is correct
3 Correct 20 ms 25172 KB Output is correct
4 Correct 16 ms 24420 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 36 ms 29428 KB Output is correct
2 Correct 43 ms 32104 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 85 ms 38148 KB Output is correct
2 Correct 85 ms 46960 KB Output is correct
3 Correct 111 ms 56440 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 132 ms 48596 KB Output is correct
2 Correct 215 ms 75756 KB Output is correct
3 Correct 204 ms 88848 KB Output is correct
4 Correct 246 ms 107948 KB Output is correct

Subtask #8
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 273 ms 83484 KB Output is correct
2 Runtime error 615 ms 131072 KB Execution killed with signal 9
3 Halted 0 ms 0 KB -

Subtask #9
0 / 10.0

# Verdict Execution time Memory Grader output
1 Runtime error 307 ms 131072 KB Execution killed with signal 9
2 Halted 0 ms 0 KB -