Submission #938049

#	Time	Username	Problem	Language	Result	Execution time	Memory
938049		asdasdqwer	Towns (IOI15_towns)	C++14	0 / 100	59 ms	1628 KiB

towns

#include "towns.h"

#include <bits/stdc++.h>
using namespace std;

#define pii array<int,2>
vector<vector<int>> dis;
map<pii,int> mp;

int query(int a, int b) {
    if (mp.find({a,b}) != mp.end()) {
        return mp[{a,b}];
    }

    if (mp.find({b,a}) != mp.end()) {
        return mp[{b,a}];
    }

    int d = getDistance(a, b);
    mp[{a,b}] = d;
    return d;
}

int hubDistance(int N, int sub) {
    dis.assign(N, vector<int>(N, 1e9));
    for (int i=0;i<N;i++) {
        dis[i][i] = 0;
    }

    // first N queries
    vector<int> lst(N);
    for (int i=0;i<N;i++) {
        lst[i] = i;
    }

    random_shuffle(lst.begin(), lst.end());

    for (int i=0;i<N;i++) {
        int a = lst[i];
        int b = lst[(i+1)%N];
        dis[a][b] = dis[b][a] = query(a,b);
    }

    // floyd warshall
    for (int k=0;k<N;k++) {
        for (int i=0;i<N;i++) {
            for (int j=0;j<N;j++) {
                dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
            }
        }
    }

    bool found = false;
    int retVal = 0;
    pii foundPos;
    while (!found) {
        // find maximum value and respective nodes
        int mxVal = -1;
        pii pos = {-1, -1};
        for (int i=0;i<N;i++) {
            for (int j=i+1;j<N;j++) {
                if (dis[i][j] > mxVal) {
                    mxVal = dis[i][j];
                    pos = {i, j};
                }
            }
        }

        int d = query(pos[0], pos[1]);

        if (d == dis[pos[0]][pos[1]]) {
            found = true;
            retVal = d;
            foundPos = pos;
            break;
        }

        dis[pos[0]][pos[1]] = dis[pos[1]][pos[0]] = d;

        for (int i=0;i<N;i++) {
            dis[i][pos[0]] = min(dis[i][pos[0]], dis[i][pos[1]] + dis[pos[1]][pos[0]]);
            dis[i][pos[1]] = min(dis[i][pos[1]], dis[i][pos[0]] + dis[pos[0]][pos[1]]);
        }
    }
    int mxDis = retVal;
    for (int i=0;i<N;i++) {
        if (i == foundPos[0] || i == foundPos[1]) continue;
        int q1 = query(foundPos[0], i);
        int q2 = query(foundPos[1], i);
        int sum = q1 + q2;
        int weightTo = (sum - retVal) / 2;
        mxDis = min(mxDis, max(q1 - weightTo, q2 - weightTo));
    }

    return mxDis;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:24:28: warning: unused parameter 'sub' [-Wunused-parameter]
   24 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 39