Submission #537347

#	Time	Username	Problem	Language	Result	Execution time	Memory
537347		ac2hu	Hotspot (NOI17_hotspot)	C++14	100 / 100	974 ms	1220 KiB

hotspot

#include <bits/stdc++.h>
#ifdef DEBUG
#include "../templates/debug.h"
#else 
#define deb(x...)
#endif
using namespace std;
#define ll long long 
#define ld long double 
const int N = 5001;
int n,m,k;
vector<int> adj[N];
int d1[N], d2[N] ,p1[N], p2[N];
ld e[N];
signed main() {
	iostream::sync_with_stdio(false);
	cin.tie(nullptr);cout.tie(nullptr);
	cout << setprecision(10);
	cin >> n >> m;
	for(int _ = 0;_<m;_++){
		int a,b;cin >> a >> b;
		// a--;b--;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	cin >> k;
	for(int _ = 0;_<k;_++){
		int s,t;cin >> s >> t;
		for(int i = 0;i<n;i++){
			d1[i] = 1e9;
			d2[i] = 1e9;
			p1[i] = 0;
			p2[i] = 0;
		}
		list<int> q;
		d1[s] = 0;
		p1[s] = 1;
		q.push_back(s);
		while(!q.empty()){
			int x = q.front();
			q.pop_front();
			// cout << x << "--> : ";
			for(int e : adj[x]){
				if(d1[e] > d1[x]){
					p1[e] += p1[x];
				}
				if(d1[e] > d1[x] + 1){
					d1[e] = d1[x] + 1;
					// cout << e << " ";
					q.push_back(e);
				}
			}
			// cout << "\n";
		}
		// cout << "\n";
		// p2 shortest paths to t
		d2[t] = 0;
		p2[t] = 1;
		q.push_back(t);
		while(!q.empty()){
			int x = q.front();
			q.pop_front();
			for(int e : adj[x]){
				if(d2[e] > d2[x])
					p2[e] += p2[x];
				if(d2[e] > d2[x] + 1){
					d2[e] = d2[x] + 1;
					q.push_back(e);
				}
			}
		}
      	assert(p1[t] == p2[s]);
		ll total = p1[t];
		// assert(p1[t] == p2[s]);
		for(int i = 0;i<n;i++){
			ll paths = p1[i]*p2[i];
			if(d1[i] + d2[i] == d1[t] && d1[t] < 1e8)
				e[i] += ((ld)paths/total);
		}
		// cout << s << " " << t << "\n";
		// cout << "distance from " << s << " to i: \n";
		// for(int i = 0;i<n;i++)
		// 	cout << d1[i] << " ";
		// cout << "\n";
		// cout << "distance from " << t << " to i: \n";
		// for(int i = 0;i<n;i++)
		// 	cout << d2[i] << " ";
		// cout << "\n";
		// cout << "paths from " << s << " to i: \n";
		// for(int i = 0;i<n;i++)
		// 	cout << p1[i] << " ";
		// cout << "\n";
		// cout << "paths from " << t << " to i: \n";
		// for(int i = 0;i<n;i++)
		// 	cout << p2[i] << " ";
		// cout << "\n";
		// cout << "------------\n";
	}
	// for(int i = 0;i<n;i++)
	// 	cout << e[i] << " ";
	// cout << "\n";
	cout << max_element(e, e + n) - e << "\n";
}

• Subtask 1: 4 / 4
• Subtask 2: 5 / 5
• Subtask 3: 11 / 11
• Subtask 4: 18 / 18
• Subtask 5: 26 / 26
• Subtask 6: 36 / 36