Submission #303937

#	Time	Username	Problem	Language	Result	Execution time	Memory
303937		fivefourthreeone	Towns (IOI15_towns)	C++17	0 / 100	20 ms	384 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>

using namespace std;

const int mxN = 111;
int arr[mxN];
int dist[mxN][mxN];
int numHub = 0;
int lcadist[mxN];
int n;
int s, t;
int getdist(int a, int b) {
    if(a==b)return 0;
    if(dist[a][b]==-1) {
        return dist[a][b] = dist[b][a] = getDistance(a, b);
    }
    return dist[a][b];
}
bool solve(int hub) {
    //cout<<hub<<" "<<lcadist[hub]<<"\n";
    vector<int> stk;
    vector<int> bkt;
    int pre = 0;
    int post = 0;
    vector<int> ch;
    for(int i = 0; i < n; ++i) {
        if(lcadist[i] > lcadist[hub])post++;
        else if(lcadist[i] < lcadist[hub])pre++;
        else ch.push_back(i);
    }
    function<bool(int, int)> compare = [&](int a, int b) {
        //cout<<a<<" "<<b<<" "<<lcadist[a]<<" "<<lcadist[b]<<" "<<lcadist[hub]<<"\n";
        if(lcadist[a] < lcadist[hub] && lcadist[b] < lcadist[hub]) {
            return true;
        }else if(lcadist[a] > lcadist[hub] && lcadist[b] > lcadist[hub]) {
            return true;   
        }else if(lcadist[a] == lcadist[hub] && lcadist[b] == lcadist[hub]) {
            if(getdist(s, a) + getdist(s, b) - getdist(a, b) > 2 * lcadist[hub])return true;
        }
        return false;
    };
    //cout<<post<<" "<<pre<<"\n";
    if(max(post, pre) > n/2) return false;
    if(ch.size() <= n/2) return true;
    for(int i: ch) {
        if(stk.empty()) {
            stk.push_back(i);
        }else if(!compare(stk.back(), i)) {
            //cout<<stk.back()<<" "<<i<<"\n";
            stk.push_back(i);
            if(bkt.size()) {
                stk.push_back(bkt.back());
                bkt.pop_back();
            }
        }else {
            bkt.push_back(i);
        }
    }
    int T = stk.back();
    while(stk.size()) {
        if(!compare(stk.back(), T)) {
            //cout<<T<<" "<<stk.back()<<"\n";
            stk.pop_back();
            if(bkt.size()) bkt.pop_back();
            else break;
        }else {
            stk.pop_back();
            if(stk.size()) stk.pop_back();
            else bkt.push_back(0);
        }
    }
    if(bkt.size() > n - ch.size())return false;
    return true;
}
int hubDistance(int N, int sub) {
    n = N;
    memset(dist, -1, sizeof(dist));
    for(int i = 1, mxdist = 0; i < n; ++i) {
        if(getdist(0, i) > mxdist) {
            mxdist = getdist(0, i);
            s = i;
        }
    }
    for(int i = 0, mxdist = 0; i < n; ++i) {
        if(i^s) {
            if(getdist(s, i) > mxdist) {
                mxdist = getdist(s, i);
                t = i;
            }
        }
    }
    int hub[2];
    int hubcnt = 0;
    int R = 0x3f3f3f3f;
    for(int i = 0; i < n; ++i) {
        lcadist[i] = (getdist(s, i) + getdist(s, 0) - getdist(i, 0)) / 2;
        if(max(lcadist[i], getdist(s, t) - lcadist[i]) < R) {
            R = max(lcadist[i], getdist(s, t) - lcadist[i]);
            hubcnt = 1;
            hub[0] = i;
        }else if(max(lcadist[i], getdist(s, t) - lcadist[i]) == R && lcadist[i]^lcadist[hub[0]]){
            hubcnt = 2;
            hub[1] = i;
        }
    }
    cout<<getdist(s, t)<<"\n";
    if(sub <= 2) {
        return R;
    }
    bool balanced = false;
    for(int i = 0; i < hubcnt; ++i) {
        balanced |= solve(hub[i]);
    }
    return (balanced ? 1 : -1) * R;
}

Compilation message (stderr)

towns.cpp: In function 'bool solve(int)':
towns.cpp:45:18: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   45 |     if(ch.size() <= n/2) return true;
      |        ~~~~~~~~~~^~~~~~

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