hdu 2665 Kth number_划分树

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题意：求区间【a，b】的第k大

因为多次询问要用到划分树

#include <iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;#define MAXN 100010int tree[30][MAXN],sorted[MAXN];int toleft[30][MAXN];void build(int l,int r,int dep){if(l==r)return;int i;int mid=(l+r)>>1;int same=mid-l+1;for(i=l;i<=r;i++)if(tree[dep][i]<sorted[mid])same--;int lpos=l;int rpos=mid+1;for(i=l;i<=r;i++){if(tree[dep][i]<sorted[mid])tree[dep+1][lpos++]=tree[dep][i];else if(tree[dep][i]==sorted[mid]&&same>0){tree[dep+1][lpos++]=tree[dep][i];same--;}elsetree[dep+1][rpos++]=tree[dep][i];toleft[dep][i]=toleft[dep][l-1]+lpos-l;//左边的个数 }build(l,mid,dep+1);build(mid+1,r,dep+1);}int query(int L,int R,int l,int r,int dep,int k){if(l==r)return tree[dep][l];int mid=(L+R)>>1;int cnt=toleft[dep][r]-toleft[dep][l-1];if(cnt>=k){int newl=L+toleft[dep][l-1]-toleft[dep][L-1];int newr=newl+cnt-1;return query(L,mid,newl,newr,dep+1,k);}else{int newr=r+toleft[dep][R]-toleft[dep][r];int newl=newr-(r-l-cnt);return query(mid+1,R,newl,newr,dep+1,k-cnt);}}int main(int argc, char** argv) {int v,n,m,i;int s,t,k;scanf("%d",&v);while(v--){scanf("%d%d",&n,&m);memset(tree,0,sizeof(tree));memset(toleft,0,sizeof(toleft));for(i=1;i<=n;i++){scanf("%d",&tree[0][i]);sorted[i]=tree[0][i];}sort(sorted+1,sorted+n+1);build(1,n,0);while(m--){scanf("%d%d%d",&s,&t,&k);printf("%d\n",query(1,n,s,t,0,k));}}return 0;}

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