Submission #1222723

#	Time	Username	Problem	Language	Result	Execution time	Memory
1222723		ByeWorld	Hotspot (NOI17_hotspot)	C++20	100 / 100	523 ms	1468 KiB

hotspot

#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define int long long
#define ll long long
#define se second
#define fi first
#define pb push_back
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<pii,pii> ipii;
const int MAXN = 5010;
const int SQRT = 450;
const int INF = 2e9;
const int MOD = 998244353;
const int LOG = 20;
int sum(int a, int b){ a%=MOD; b%=MOD; return (a+MOD+b)%MOD; }
void chsum(int &a, int b){ a%=MOD; b%=MOD; a = (a+MOD+b)%MOD; }
int mul(int a, int b){ return (a*b)%MOD; }
int expo(int a, int b){
	if(b==0) return 1;
	int te = expo(a, b/2); te = mul(te,te);
	return (b%2 ? mul(te,a) : te);
}
void chmul(int &a, int b){ a = (a*b)%MOD; }
void chmn(auto &a, auto b){ a = min(a, b); }
void chmx(auto &a, auto b){ a = max(a, b); }

int n, m, dis[MAXN], dis2[MAXN], dp[MAXN], dp2[MAXN];
ld num[MAXN];
vector<int> adj[MAXN];

void dji(int sta, int en){
	for(int i=1; i<=n; i++) dis[i] = INF, dp[i] = 0;
	queue <int> q;
	dis[sta] = 0; q.push(sta); dp[sta] = 1;
	while(!q.empty()){
		int nw = q.front(); q.pop();
		for(auto nx : adj[nw]){
			if(dis[nx] > dis[nw]+1){
				dp[nx] = dp[nw];
				dis[nx] = dis[nw]+1;
				q.push(nx);
			} else if(dis[nx] == dis[nw]+1)
				dp[nx] += dp[nw];
		}
	}

	for(int i=1; i<=n; i++) dis2[i] = INF, dp2[i] = 0;
	dis2[en] = 0; q.push(en); dp2[en] = 1;
	while(!q.empty()){
		int nw = q.front(); q.pop();
		for(auto nx : adj[nw]){
			if(dis2[nx] > dis2[nw]+1){
				dp2[nx] = dp2[nw];
				dis2[nx] = dis2[nw]+1;
				q.push(nx);
			} else if(dis2[nx] == dis2[nw]+1)
				dp2[nx] += dp2[nw];
		}
	}

	int way = dp[en];
// 	assert(way==1);
	for(int i=1; i<=n; i++){
		if(dis[i]+dis2[i] == dis[en]){
			num[i] += (ld)dp[i]*dp2[i]/way;
		}
	}
}
signed main(){
	ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n>>m;
	for(int i=1; i<=m; i++){
		int x, y; cin>>x>>y; x++; y++;
		adj[x].pb(y); adj[y].pb(x);
	}
	int k; cin>>k;
	for(int i=1; i<=k; i++){
		int x, y; cin>>x>>y; x++; y++;
		dji(x, y);
	}
	int idx = 0;
	for(int i=1; i<=n; i++) 
		if(num[idx] < num[i]) idx = i;
	cout << idx-1 << '\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