Submission #714857

#	Time	Username	Problem	Language	Result	Execution time	Memory
714857		lam	Towns (IOI15_towns)	C++14	0 / 100	16 ms	556 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
#define ff first
#define ss second
const int maxn = 510;
int n;
int d[maxn][maxn];
int ds[maxn],up[maxn];
map<ii,int> cnt;
int Ask(int u, int v)
{
    if (u==v) return 0;
    if (u>v) swap(u,v);
    if (d[u][v] == -1)
    {
        d[u][v] = getDistance(u,v);
    }
    return d[u][v];
}
bool check(int dist)
{
    vector<int> to_mid(n+1,0);
    for (int i=0; i<n; i++)
        if (ds[i]<dist) to_mid[i]=dist-ds[i]+up[i];
    else to_mid[i]=ds[i]-dist+up[i];
    vector <int> sz(n+1,0);
    int alive = 0; int num=1;
    for (int i=1; i<n; i++)
        if (num==0)
    {
        num=1;
        sz[i]++; alive=i;
    }
    else
    {
        if (Ask(i,alive)==to_mid[i]+to_mid[alive])
        {
            num--; sz[i]++;
        }
        else
        {
            num++;
            sz[alive]++;
        }
    }
    if (num<=0) return 1;
    num=0;
    for (int i=0; i<n; i++) if (sz[i]!=0)
    {
        if (Ask(i,alive)==to_mid[i]+to_mid[alive]) num-=sz[i];
        else num+=sz[i];
    }
    return num<=0;
}

int hubDistance(int N, int sub) {
    n=N;
    cnt.clear();
    for (int i=0; i<n; i++)
        for (int j=0; j<n; j++) d[i][j] = -1;
    int u,v,dist;
    u=0;
    for (int i=1; i<n; i++) if (dist<Ask(0,i))
    {
        u=i;
        dist=Ask(0,i);
    }
    v=0; dist=0;
    for (int i=1; i<n; i++) if (dist<Ask(u,i))
    {
        dist=Ask(u,i);
        v=i;
    }
    int R=1e9;
    for (int i=0; i<n; i++)
    {
        int x=Ask(u,i); int y=Ask(i,v);
        int z=Ask(u,v);
        up[i] = (x+y-z)/2;
        ds[i] = Ask(u,i)-up[i];
        R=min(R,max(ds[i],Ask(u,v)-ds[i]));
        cnt[{ds[i],Ask(u,v)-ds[i]}]++;
    }
    int sum = 0;
    int it = -1;
    int dau = 1;
    for (auto i:cnt)
    {
        int sz = i.ss;
        if (max(i.ff.ff,i.ff.ss)==R)
        {
            if (sz<=n/2&&sum<=n/2&&(n-sz-sum<=n/2))
            {
                dau=1;
                it=-1;
                break;
            }
            else if (sum<=n/2&&(n-sz-sum)<=n/2)
            {
                it=i.ff.ff;
            }
        }
        sum+=sz;
    }
    if (it!=-1)
    {
        if (check(it)) dau=1;
        else dau=-1;
    }
//    cerr<<R<<endl;
    return dau*R;

}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:59:28: warning: unused parameter 'sub' [-Wunused-parameter]
   59 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~
towns.cpp:66:29: warning: 'dist' may be used uninitialized in this function [-Wmaybe-uninitialized]
   66 |     for (int i=1; i<n; i++) if (dist<Ask(0,i))
      |                             ^~

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