OJ-Problems-Source/HDOJ/3845_autoAC.cpp

#include <cstdio>
#include <cstring>
#include <algorithm>
#define PI pair<int, int>
#define MP make_pair
#define x first
#define y second
const int maxn = 100100;
using namespace std;
int N, m;
inline bool in( int x, int y )
{
    return x >= -m && x <= m && y >= -m && y <= m;
}
PI p[maxn];
PI a[maxn], b[maxn], c[maxn], d[maxn];
int ea, eb, ec, ed;
bool chk()
{
    int i, j, k;
    ea = eb = ec = ed = -1;
    for( i = 0; i < N; ++i )
    {
        if( in(p[i].x+m, p[i].y-m) )
        {
            while( ea >= 0 && a[ea].y >= p[i].y-m )    ea--;
            if( ea >= 0 && a[ea].x==p[i].x+m )    continue;
            a[++ea] = MP(p[i].x+m, p[i].y-m);
        }
        if( in(p[i].x+m, p[i].y+m) )
        {
            while( eb >= 0 && b[eb].y <= p[i].y+m )    eb--;
            if( eb >= 0 && b[eb].x==p[i].x+m )    continue;
            b[++eb] = MP(p[i].x+m, p[i].y+m);
        }
    }
    for( i = N-1; i >= 0; --i )
    {
        if( in(p[i].x-m, p[i].y-m) )
        {
            while( ec >= 0 && c[ec].y >= p[i].y-m )    ec--;
            if( ec >= 0 && c[ec].x==p[i].x-m )    continue;
            c[++ec] = MP(p[i].x-m, p[i].y-m);
        }
        if( in(p[i].x-m, p[i].y+m) )
        {
            while( ed >= 0 && d[ed].y <= p[i].y+m )    ed--;
            if( ed >= 0 && d[ed].x==p[i].x-m )    continue;
            d[++ed] = MP(p[i].x-m, p[i].y+m);
        }
    }
    int na = 0, nb = 0, nc = ec+1, nd = ed+1;
    int v1, v2;
    for( i = -m; i <= m; ++i )
    {
        if( nc > 0 && c[nc-1].x == i )    nc--;
        if( nd > 0 && d[nd-1].x == i )    nd--;
        v1 = m+1, v2 = -m-1;
        if( na <= ea )    v1 = min(v1, a[na].y);
        if( nb <= eb )    v2 = max(v2, b[nb].y);
        if( nc <= ec )    v1 = min(v1, c[nc].y);
        if( nd <= ed )    v2 = max(v2, d[nd].y);
        if( v1-1 > v2 )    return 0;
        if( na <= ea && a[na].x == i )    na++;
        if( nb <= eb && b[nb].x == i )    nb++;
    }
    return 1;
}
int main()
{
    int i, j, k, cases = 1;
    int ll, rr;
    while( scanf("%d", &N), N+1 )
    {
        for( i = 0; i < N; ++i )
            scanf("%d %d", &p[i].x, &p[i].y);
        sort(p, p+N);
        ll = -1, rr = 1000000;
        while( rr-ll > 1 )
        {
            m = (ll+rr)/2;
            if( chk() )
                rr = m;
            else
                ll = m;
        }
        m = rr;
        printf("Case %d: ", cases++);
        if( chk() )    printf("%d\n", rr);
        else    puts("never");
    }
    return 0;
}