Submission #386099

#	Time	Username	Problem	Language	Result	Execution time	Memory
386099		cpp219	Race (IOI11_race)	C++14	100 / 100	1053 ms	33644 KiB

race

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
#define pb push_back
#define mp make_pair
#define pii pair <int, int>
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define F first
#define S second
 
const int maxn = 2e5 + 5, maxk = 1e6 + 5;
vector <pii> adj[maxn];
int w[maxn], sz[maxn];
int h[maxn], d[maxn], mn[maxk];
int n, k;
int inf = 1e9 + 7, ans = 1e9 + 7;
bool dead[maxn];
 
void dfs(int v, int p = -1){
	sz[v] = 1;
	for(auto u : adj[v]){
		if(u.F != p && !dead[u.F]){
			d[u.F] = d[v] + w[u.S];
			h[u.F] = h[v] + 1;
			dfs(u.F, v);
			sz[v] += sz[u.F]; 
		}
	}
}
int find_centroid(int v, int p, int z){
	for(auto u : adj[v]){
		if(u.F != p && !dead[u.F] && sz[u.F] > z / 2){
			return find_centroid(u.F, v, z);
		}
	}
	return v;
}
 
void get(int v, int p = -1){
	if(k - d[v] >= 0 && k - d[v] < maxk - 2){
		ans = min(mn[k - d[v]] + h[v], ans);
	}
	for(auto u : adj[v]){
		if(u.F != p && !dead[u.F]){
			get(u.F, v);
		}
	}
}
void upd(int v, int p = -1){
	if(d[v] >= 0 && d[v] < maxk - 2){
		mn[d[v]] = min(h[v], mn[d[v]]);
	}
	for(auto u : adj[v]){
		if(u.F != p && !dead[u.F]){
			upd(u.F, v);
		}
	}
}
void clr(int v, int p = -1){
	if(d[v] >= 0 && d[v] < maxk - 2){
		mn[d[v]] = inf;
	}
	for(auto u : adj[v]){
		if(u.F != p && !dead[u.F]){
			clr(u.F, v);
		}
	}
}
 
void solve(int v){
	dfs(v);
	int c = find_centroid(v, -1, sz[v]);
	dead[c] = true;
	h[c] = d[c] = 0;
	dfs(c);
	for(auto x : adj[c]){
		int u = x.F;
		if(!dead[u]){
			get(u, c);
			upd(u, c);
		}
	}
	ans = min(ans, mn[k]);
	clr(c);
	for(auto x : adj[c]){
		if(!dead[x.F]){
			solve(x.F);
		}
	}
}
int best_path(int N, int K, int H[][2], int L[]){
	n = N;
	k = K;
	
	for(int i = 0; i < n - 1; i ++){
		int x = H[i][0], y = H[i][1];
		adj[x].push_back({y, i});
		adj[y].push_back({x, i});
	}	
	for(int i = 0; i < n - 1; i ++)
		w[i] = L[i];
	
	for(int i = 0; i < maxk - 2; i ++){
		mn[i] = inf;
	}
	
	solve(0);
 
	if(ans >= inf){
		ans = -1;
	}
		
	return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57