bzoj1941

Posted 2020-10-15 123456

KD-tree

**了这道题

这个估价函数好鬼畜，把min打成max。。。

关于min的估价函数非常鬼畜，具体我也不知道为什么。

#include<bits/stdc++.h>
using namespace std;
const int N = 5e5 + 5;
int n, d, root, ans = 2e9, mx, mn;
struct data {
    int x, y, mxx, mnx, mny, mxy, lc, rc;
    bool friend operator < (const data &a, const data &b) {
        if(d == 0) return a.x == b.x ? a.y < b.y : a.x < b.x;
        if(d == 1) return a.y == b.y ? a.x < b.x : a.y < b.y;
    }
} a[N];
void update(int x)
{
    a[x].mnx = min(a[x].x, min(a[a[x].lc].mnx, a[a[x].rc].mnx));
    a[x].mxx = max(a[x].x, max(a[a[x].lc].mxx, a[a[x].rc].mxx));
    a[x].mny = min(a[x].y, min(a[a[x].lc].mny, a[a[x].rc].mny));
    a[x].mxy = max(a[x].y, max(a[a[x].lc].mxy, a[a[x].rc].mxy)); 
}
int build(int l, int r, int D)
{
    if(l > r) return 0;
    int mid = (l + r) >> 1;
    nth_element(a + l, a + mid, a + r + 1);
    a[mid].mnx = a[mid].mxx = a[mid].x;
    a[mid].mny = a[mid].mxy = a[mid].y;
    a[mid].lc = build(l, mid - 1, D ^ 1);
    a[mid].rc = build(mid + 1, r, D ^ 1);
    update(mid);
    return mid;
}
int query_mn(int k, int x, int y)
{
    int d = abs(a[k].x - x) + abs(a[k].y - y), 
    dl = a[k].lc ? max(a[a[k].lc].mnx - x, 0) + max(x - a[a[k].lc].mxx, 0) + max(a[a[k].lc].mny - y, 0) + max(y - a[a[k].lc].mxy, 0) : 5e8, 
    dr = a[k].rc ? max(a[a[k].rc].mnx - x, 0) + max(x - a[a[k].rc].mxx, 0) + max(a[a[k].rc].mny - y, 0) + max(y - a[a[k].rc].mxy, 0) : 5e8;
    if(d) mn = min(mn, d);
    if(dl < dr) 
    {
        if(mn > dl) query_mn(a[k].lc, x, y);
        if(mn > dr) query_mn(a[k].rc, x, y);
    } 
    else
    {
        if(mn > dr) query_mn(a[k].rc, x, y);
        if(mn > dl) query_mn(a[k].lc, x, y);     
    }
}
int query_mx(int k, int x, int y)
{
    int d = abs(a[k].x - x) + abs(a[k].y - y), 
    dl = a[k].lc ? max(abs(a[a[k].lc].mnx - x), abs(a[a[k].lc].mxx - x)) + max(abs(a[a[k].lc].mny - y), abs(a[a[k].lc].mxy - y)) : -5e8, 
    dr = a[k].rc ? max(abs(a[a[k].rc].mnx - x), abs(a[a[k].rc].mxx - x)) + max(abs(a[a[k].rc].mny - y), abs(a[a[k].rc].mxy - y)) : -5e8;
    if(d) mx = max(mx, d);
    if(dl > dr) 
    {
        if(mx < dl) query_mx(a[k].lc, x, y);
        if(mx < dr) query_mx(a[k].rc, x, y);
    } 
    else
    {
        if(mx < dr) query_mx(a[k].rc, x, y);
        if(mx < dl) query_mx(a[k].lc, x, y);     
    }
}
int main()
{
    a[0].mnx = a[0].mny = 5e8;
    a[0].mxx = a[0].mxy = -5e8;
    scanf("%d", &n);
    for(int i = 1; i <= n; ++i) scanf("%d%d", &a[i].x, &a[i].y);
    root = build(1, n, 0);
    for(int i = 1; i <= n; ++i) 
    {
        mx = -5e8;
        mn = 5e8;
        query_mn(root, a[i].x, a[i].y);
        query_mx(root, a[i].x, a[i].y);
        ans = min(ans, mx - mn);
    }
    printf("%d\\n", ans);
    return 0;
}

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