poj2104 主席树 区间K大 在线 无修改

 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 const int maxn = 100000 + 100;
 5 
 6 int id[maxn], root[maxn], a[maxn], b[maxn], n, m, size;
 7 struct chairman_tree_node {
 8     int ls, rs, w;
 9 } T[maxn * 23];
10 void insert(int l, int r, int &pos, int val) {
11     T[++size] = T[pos], pos = size;
12     ++T[pos].w;
13     if(l == r) return ;
14     int mid = (l + r) >> 1;
15     if(val <= mid) insert(l, mid, T[pos].ls, val);
16     else insert(mid + 1, r, T[pos].rs, val);
17 }
18 int query(int p, int q, int l, int r, int k) {
19     if(l == r) return l;
20     int t = T[T[q].ls].w - T[T[p].ls].w;
21     int mid = (l + r) >> 1;
22     if(k <= t) return query(T[p].ls, T[q].ls, l, mid, k);
23     else return query(T[p].rs, T[q].rs, mid + 1, r, k - t);
24 }
25 bool cmp(int x, int y) {
26     return a[x] < a[y];
27 }
28 int main() {
29     scanf("%d%d", &n, &m);
30     for(int i = 1; i <= n; ++i) {
31         scanf("%d", &a[i]);
32         id[i] = i;
33     }
34     sort(id + 1, id + n + 1, cmp);
35     for(int i = 1; i <= n; ++i) {
36         b[id[i]] = i;
37     }
38     for(int i = 1; i <= n; ++i) {
39         root[i] = root[i - 1];
40         insert(1, n, root[i], b[i]);
41     }
42     for(int i = 1; i <= m; ++i) {
43         int l, r, k;
44         scanf("%d%d%d", &l, &r, &k);
45         printf("%d\n", a[id[query(root[l - 1], root[r], 1, n, k)]]);
46     }
47     return 0;
48 }