Submission #710474

#	Time	Username	Problem	Language	Result	Execution time	Memory
710474		That_Salamander	Traffic (IOI10_traffic)	C++14	100 / 100	1118 ms	131632 KiB

traffic

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <cstring>
#include <queue>
#include <unordered_set>
#include <unordered_map>
#include <chrono>

#define FOR(var,bound) for(int var = 0; var < bound; var++)
#define FORB(var,lb,ub) for (int var = lb; var < ub; var++)
#define FORR(var,bound) for(int var = bound-1; var >= 0; var--)

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef pair<int, int> pii;

vvi conn;
vector<signed> p;
vector<int> dp(1000000);

int bestNode = -1;
int bestVal = 2000000005;

int dfs1(int n, int par) {
    int res = p[n];

    for (int x: conn[n]) {
        if (x != par) {
            res += dfs1(x, n);
        }
    }

    return dp[n] = res;
}

void reroot(int oldRoot, int newRoot) {
    dp[oldRoot] -= dp[newRoot];
    dp[newRoot] += dp[oldRoot];
}

void dfs2(int n, int par) {
    int traffic = 0;

    for (int x: conn[n]) {
        traffic = max(traffic, dp[x]);

        if (x == par) continue;

        reroot(n, x);
        dfs2(x, n);
        reroot(x, n);
    }

    if (traffic < bestVal) {
        bestVal = traffic;
        bestNode = n;
    }

#ifdef LOCAL_TEST
    //cout << n << " -> " << traffic << endl;
#endif
}

int LocateCentre(int N, int* P, int* S, int* D) {
    p.resize(N);

    FOR(i, N) p[i] = P[i];

    conn.resize(N);

    FOR(i, N - 1) {
        conn[S[i]].push_back(D[i]);
        conn[D[i]].push_back(S[i]);
    }

    int m = N / 2;

    dfs1(m, -1);
    dfs2(m, -1);

    return bestNode;
}

#ifdef LOCAL_TEST
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    srand(NULL);

    int n;

    //cin >> n;
    n = 1000000;

    vi p(n), s(n-1), d(n-1);

    FOR(i, n) {
        //cin >> p[i];
        p[i] = rand() % 2000;
    }

    FOR(i, n -1) {
        //cin >> s[i] >> d[i];
        s[i] = i;
        d[i] = i + 1;
    }

    auto start = chrono::high_resolution_clock::now();
    cout << LocateCentre(n, p.data(), s.data(), d.data()) << endl;
    auto end = chrono::high_resolution_clock::now();

    cout << chrono::duration_cast<chrono::milliseconds>(end - start).count() << endl;
}
#endif

• Subtask 1: 25 / 25
• Subtask 2: 25 / 25
• Subtask 3: 25 / 25
• Subtask 4: 25 / 25