Submission #672946

#	Time	Username	Problem	Language	Result	Execution time	Memory
672946		vuavisao	Hotspot (NOI17_hotspot)	C++14	100 / 100	843 ms	1260 KiB

hotspot

#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
#define ld long double
using namespace std;

template<typename Lhs, typename Rhs> inline bool Max_self(Lhs &a, Rhs b) { if(b > a) { a = b; return true; } return false; }
template<typename Lhs, typename Rhs> inline bool Min_self(Lhs &a, Rhs b) { if(b < a) { a = b; return true; } return false; }

const int N = 5e3 + 10;
const int INF = 1e9;

int n, m, q;
vector<int> g[N];

int dist[2][N];
ld cnt[2][N];
ld res[N];

void Dijkstra(int u, int* dist, ld* cnt);
void Dijkstra(int u, int* dist, ld* cnt) {
    for(int i = 1; i <= n; ++ i) {
        dist[i] = INF;
        cnt[i] = 0;
    }
    dist[u] = 0; cnt[u] = 1;
    queue<int> q = {};
    q.push(u);
    while(!q.empty()) {
        int u = q.front(); q.pop();
        for(const auto& v : g[u]) {
            if(Min_self(dist[v], dist[u] + 1)) {
                cnt[v] = cnt[u];
                q.push(v);
            }
            else if(dist[v] == dist[u] + 1) {
                cnt[v] += cnt[u];
            }
        }
    }
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen("NOI17_hotspot.inp", "r")) {
        freopen("NOI17_hotspot.inp", "r", stdin);
        freopen("NOI17_hotspot.out", "w", stdout);
    }
    cin >> n >> m;
    for(int i = 1; i <= m; ++ i) {
        int u, v; cin >> u >> v;
        ++ u; ++ v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    cin >> q;
    while(q--) {
        int u, v; cin >> u >> v; ++ u; ++ v;
        Dijkstra(u, dist[0], cnt[0]);
        Dijkstra(v, dist[1], cnt[1]);
        for(int i = 1; i <= n; ++ i) {
//            cout << dist[0][i] << ' ' << dist[1][i] << '\n';
            if(dist[0][i] + dist[1][i] == dist[0][v]) {
                res[i] += cnt[0][i] * cnt[1][i] / cnt[0][v];
            }
        }
    }
    cout << max_element(res + 1, res + 1 + n) - res - 1;
    return 0;
}

/// Code by vuavisao

Compilation message (stderr)

hotspot.cpp: In function 'int32_t main()':
hotspot.cpp:49:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |         freopen("NOI17_hotspot.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
hotspot.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen("NOI17_hotspot.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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