POJ 2104 K-th Number 划分树

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题目大意：给定一个序列，每次询问区间第k小

BZOJ又维护。。。尼玛，题写完交不上去，各种虐心。。。。。只能去学学其它的数据结构了0.0

静态序列求区间第k小，典型的划分树，具体写法直接见百度，这里不加累述

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>#define M 100100using namespace std;int n,m,a[M],b[M],c[M];int s[20][M];void Build_Tree(int l,int r,int dpt){int i,mid=l+r>>1;if(l==r)return ;int l1=l,l2=mid+1;for(i=l;i<=r;i++){if(a[i]>c[mid]||a[i]==c[mid]&&l1>mid)b[l2++]=a[i],s[dpt][i]=(i==l?0:s[dpt][i-1]  );elseb[l1++]=a[i],s[dpt][i]=(i==l?1:s[dpt][i-1]+1);}memcpy( a+l , b+l , sizeof(a[0])*(r-l+1) );Build_Tree(l,mid,dpt+1);Build_Tree(mid+1,r,dpt+1);}int getans(int l,int r,int dpt,int x,int y,int k){int mid=l+r>>1;if(l==r)return c[mid];int l1=(x==l?0:s[dpt][x-1]),l2=s[dpt][y];if(k<=l2-l1)return getans(l,mid,dpt+1,l+l1,l+l2-1,k);elsereturn getans(mid+1,r,dpt+1,(mid+1)+(x-l-l1),(mid+1)+(y-l+1-l2)-1,k-l2+l1);}int main(){int i,x,y,k;cin>>n>>m;for(i=1;i<=n;i++)scanf("%d",&a[i]),c[i]=a[i];sort(c+1,c+n+1);Build_Tree(1,n,0);for(i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&k);printf("%d\n", getans(1,n,0,x,y,k) );}}

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