hdu 4417 划分树

思路：二分枚举区间第k大。用划分树查找是否符合要求的高度。

#include<iostream>

#include<algorithm>

#include<cstdio>

#include<cmath>

#include<cstring>

#define Maxn 100010

#define lson(x) x<<1

#define rson(x) x<<1|1

#define mid ((tree[po].l+tree[po].r)>>1)

using namespace std;

int val[20][Maxn],toLeft[20][Maxn],sorted[Maxn];

struct Tree{

    int l,r;

}tree[Maxn*4];

void BuildTree(int l,int r,int dep,int po)

{

    tree[po].l=l,tree[po].r=r;

    if(l==r)

        return ;

    int same=mid-l+1,i;

    for(i=l;i<=r;i++)

        if(val[dep][i]<sorted[mid])

        same--;

    int lpos=l,rpos=mid+1;

    for(i=l;i<=r;i++){

        if(i==l)

        toLeft[dep][i]=0;

        else

        toLeft[dep][i]=toLeft[dep][i-1];

        if(val[dep][i]<sorted[mid])

            toLeft[dep][i]++,val[dep+1][lpos++]=val[dep][i];

        else

        if(val[dep][i]>sorted[mid])

            val[dep+1][rpos++]=val[dep][i];

        else

            if(same)

            toLeft[dep][i]++,val[dep+1][lpos++]=val[dep][i],same--;

            else

            val[dep+1][rpos++]=val[dep][i];

    }

    BuildTree(l,mid,dep+1,lson(po));

    BuildTree(mid+1,r,dep+1,rson(po));

}

int query(int l,int r,int k,int dep,int po)

{

    if(l==r)

        return val[dep][l];

    int vd,invd;

    if(l==tree[po].l){

        vd=toLeft[dep][r];

        invd=0;

    }

    else{

        vd=toLeft[dep][r]-toLeft[dep][l-1];

        invd=toLeft[dep][l-1];

    }

    if(vd>=k){

        int newl=invd+tree[po].l;

        int newr=invd+vd+tree[po].l-1;

        return query(newl,newr,k,dep+1,lson(po));

    }

    else{

        int ss=l-tree[po].l-invd;

        int s=r-l+1-vd;

        int newl=mid+ss+1;

        int newr=mid+ss+s;

        return query(newl,newr,k-vd,dep+1,rson(po));

    }

}

int solve(int s,int t,int x)

{

    int i,j,l,r,Mid;

    l=0,r=t-s+1;

    while(l+1<r){

        Mid=(l+r)>>1;

        int temp=query(s,t,Mid,0,1);

        if(temp>x)

            r=Mid-1;

        else

            l=Mid;

    }

    if(r>=1)

    if(query(s,t,r,0,1)<=x)

        return r;

    return l;

}

int main()

{

    int n,m,i,j,l,r,Case=0,t,x;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%d%d",&n,&m);

        for(i=1;i<=n;i++){

            scanf("%d",&val[0][i]);

            sorted[i]=val[0][i];

        }

        sort(sorted+1,sorted+1+n);

        BuildTree(1,n,0,1);

        printf("Case %d:\n",++Case);

        for(i=1;i<=m;i++){

            scanf("%d%d%d",&l,&r,&x);

            l++,r++;

            printf("%d\n",solve(l,r,x));

        }

    }

    return 0;

}