BZOJ 2716 [Violet 3]天使玩偶 (CDQ分治、树状数组)

题目链接: https://www.lydsy.com/JudgeOnline/problem.php?id=2716

怎么KD树跑得都那么快啊。。我写的CDQ分治被暴虐

做四遍CDQ分治，每次求一个左下角\(x_i+y_i\)的最大值

第一种写法是一开始按时间排序，然后CDQ分治的时候改成按\(x\)坐标排序，同时用树状数组统计每个\(y\)坐标的最大值

第二种写法是一开始按\(x\)坐标排序，然后CDQ分支的时候改成按时间排序

CDQ分治好神奇(琦)。。。

一定要注意树状数组如果没有元素不能返回0! 我这么写然后test1 WA on line 40W+...

代码

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cassert>
#include<algorithm>
using namespace std;

const int N = 1e6;
const int C = 1e6+2;
struct Query
{
    int opt,x,y,id,ans;
    bool operator <(const Query &arg) const {return id<arg.id;}
} qr[N+3],qr2[N+3];
int tr[C+3];
int n,q,mx;

void modify(int lrb,int val)
{
    while(lrb<=mx)
    {
        tr[lrb] = max(tr[lrb],val);
        lrb += (lrb&(-lrb));
    }
}

int querymax(int rb)
{
    int ret = -C*2;
    while(rb>0)
    {
        ret = max(ret,tr[rb]);
        rb -= (rb&(-rb));
    }
    return ret;
}

void clear(int lrb)
{
    while(lrb<=mx && tr[lrb]!=-C*2)
    {
        tr[lrb] = -C*2;
        lrb += (lrb&(-lrb));
    }
}

void cdqdc(int lb,int rb)
{
    if(lb==rb) return;
    int mid = (lb+rb)>>1;
    int j = lb,k = mid+1;
    for(int i=lb; i<=rb; i++)
    {
        if(qr[i].id<=mid) {qr2[j] = qr[i]; j++;}
        else {qr2[k] = qr[i]; k++;}
    }
    for(int i=lb; i<=rb; i++) qr[i] = qr2[i];
    cdqdc(lb,mid);
    cdqdc(mid+1,rb);
    j = lb; k = mid+1;
    while(k<=rb)
    {
        while(j<=mid && qr[j].opt==2) j++;
        while(k<=rb && qr[k].opt==1) k++;
        if(k>rb) break;
        while(j<=mid && qr[j].x<=qr[k].x)
        {
            if(qr[j].opt==1) {modify(qr[j].y,qr[j].x+qr[j].y);}
            j++;
        }
        int tmp = querymax(qr[k].y);
        qr[k].ans = min(qr[k].ans,qr[k].x+qr[k].y-tmp);
        k++;
    }
    for(int i=lb; i<=mid; i++) {if(qr[i].opt==1) clear(qr[i].y);}
    j = lb; k = mid+1;
    for(int i=lb; i<=rb; i++)
    {
        if(j>mid || (k<=rb && qr[k].x<qr[j].x)) {qr2[i] = qr[k]; k++;}
        else {qr2[i] = qr[j]; j++;}
    }
    for(int i=lb; i<=rb; i++) qr[i] = qr2[i];
}

int main()
{
    scanf("%d%d",&n,&q);
    for(int i=1; i<=n; i++)
    {
        scanf("%d%d",&qr[i].x,&qr[i].y); qr[i].opt = 1; qr[i].id = i; qr[i].x++; qr[i].y++; qr[i].ans = C*7;
        mx = max(mx,max(qr[i].x,qr[i].y));
    }
    for(int i=n+1; i<=n+q; i++)
    {
        scanf("%d%d%d",&qr[i].opt,&qr[i].x,&qr[i].y,&qr[i].opt); qr[i].id = i; qr[i].x++; qr[i].y++; qr[i].ans = C*7;
        mx = max(mx,max(qr[i].x,qr[i].y));
    }
    q+=n;
    for(int i=0; i<=mx; i++) tr[i] = -C*2;
    cdqdc(1,q);
    sort(qr+1,qr+q+1);
    for(int i=1; i<=q; i++) {qr[i].x = mx+1-qr[i].x;}
    cdqdc(1,q);
    sort(qr+1,qr+q+1);
    for(int i=1; i<=q; i++) {qr[i].y = mx+1-qr[i].y;}
    cdqdc(1,q);
    sort(qr+1,qr+q+1);
    for(int i=1; i<=q; i++) {qr[i].x = mx+1-qr[i].x;}
    cdqdc(1,q);
    sort(qr+1,qr+q+1);
    for(int i=1; i<=q; i++)
    {
        if(qr[i].opt==2) printf("%d\n",qr[i].ans);
    }
    return 0;
}

标签：排序,2716,int,分治,CDQ,rb,Violet,include
来源： https://www.cnblogs.com/suncongbo/p/11096181.html