Weight segment tree Luo Valley 1168

This question seems more than a tree line weights practice;

But I am using weights to solve the tree line, because the data is open to the 1e9, so you have to discrete.

After discretization, Build first, the digital recording of the size range of each node contains,

Then slowly achievements, achievements in the process, when a single number, it queries;

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<math.h>
 4 #include<string.h>
 5 #include<queue>
 6 using namespace std;
 7 const int maxn=1e5+10;
 8 int a[maxn],b[maxn];
 9 struct node
10 {
11     int l,r,mid;
12     int num;
13 }tree[maxn<<2];
14 void build(int l,int r,int cur)
15 {
16     tree[cur].l=l,tree[cur].r=r;
17     tree[cur].num=0;
18     tree[cur].mid=(l+r)/2;
19     if(l==r) return;
20     build(l,tree[cur].mid,cur<<1);
21     build(tree[cur].mid+1,r,cur<<1|1);
22 }
23 void update(int pos,int cur)
24 {
25     tree[cur].num++;
26     if(tree[cur].l==tree[cur].r) return;
27     if(pos<=tree[cur].mid)
28         update(pos,cur<<1);
29     else update(pos,cur<<1|1);
30 }
31 int query(int base,int cur)
32 {
33     if(tree[cur].l==tree[cur].r) return tree[cur].l;
34     if(base<=tree[cur<<1].num) return (query(base,cur<<1));
35     else return (query(base-tree[cur<<1].num,cur<<1|1));
36 }
37 int main()
38 {
39     int n;
40     scanf("%d",&n);
41     for(int i=1;i<=n;i++){
42         scanf("%d",&a[i]);
43         b[i]=a[i];
44     }
45     sort(b+1,b+1+n);
46     int t=unique(b+1,b+1+n)-b-1;
47     build(1,n,1);
48     for(int i=1;i<=n;i++){
49         int pos=lower_bound(b+1,b+1+t,a[i])-b;
50         update(pos,1);
51         if(i%2) printf("%d\n",b[query(i/2+1,1)]);
52     }
53     return 0;
54 }