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

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#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;
}