划分树

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 const int MAXN = 100010;
 7 int tree[20][MAXN];//表示每层每个位置的值
 8 int sorted[MAXN];//已经排序好的数
 9 int toleft[20][MAXN];//toleft[p][i]表示第p层从1到i有多少数分入左边
10 void build(int l,int r,int dep)
11 {
12     if(l == r)return;
13     int mid = (l+r)>>1;
14     int same = mid  - l + 1;//表示等于中间值而且被分入左边的个数
15     for(int  i = l; i <= r; i++)  //注意是l,不是one
16     if(tree[dep][i] < sorted[mid])
17     same--;
18     int lpos = l;
19     int rpos = mid+1;
20     for(int i = l;i <= r;i++)
21     {
22         if(tree[dep][i] < sorted[mid])
23             tree[dep+1][lpos++] = tree[dep][i];
24         else if(tree[dep][i] == sorted[mid] && same > 0)
25         {
26             tree[dep+1][lpos++] =  tree[dep][i];
27             same--;
28         }
29         else
30             tree[dep+1][rpos++] = tree[dep][i];
31         toleft[dep][i] = toleft[dep][l-1] + lpos  - l;
32     }
33     build(l,mid,dep+1);
34     build(mid+1,r,dep+1);
35 }
36 
37 int query(int L,int R,int l,int r,int dep,int k)
38 {
39     if(l==r)return tree[dep][l];
40     int mid=(L+R)>>1;
41     int cnt=toleft[dep][r]-toleft[dep][l-1];
42     if(k<=cnt)
43     {
44         int newl=L+toleft[dep][l-1]-toleft[dep][L-1];
45         int newr=newl+cnt-1;
46         return query(L,mid,newl,newr,dep+1,k);
47     }
48     else
49     {
50         int newr=r+toleft[dep][R]-toleft[dep][r];
51         int newl=newr-(r-l-cnt);
52         return query(mid+1,R,newl,newr,dep+1,k-cnt);
53     }
54 }
55 int main()
56 {
57     int n,m;
58     while(scanf("%d%d",&n,&m)!=EOF)
59     {
60         memset(tree,0,sizeof(tree));
61         for(int i = 1;i <= n;i++)
62         {
63             scanf("%d",&tree[0][i]);
64             sorted[i] = tree[0][i];
65         }
66         sort(sorted+1,sorted+n+1);
67         build(1,n,0);
68         int s,t,k;
69         while(m--)
70         {
71             scanf("%d%d%d",&s,&t,&k);
72             printf("%d\n",query(1,n,s,t,0,k));
73         }
74     }
75     return 0;
76 }