poj2104 划分树 区间K大 在线 无修改

 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 const int maxn = 100000 + 10;
 5 int val[20][maxn], sorted[maxn], to_left[20][maxn];
 6 int n, m;
 7 void build_tree(int l, int r, int layer) {
 8     if(l == r) return ;
 9     int mid = (l + r) >> 1;
10     int suppose = mid - l + 1;
11     for(int i = l; i <= r; ++i)
12         if(val[layer][i] < sorted[mid])
13             --suppose;
14     int rec_l = l, rec_r = mid + 1;
15     for(int i = l; i <= r; ++i) {
16         if(i == l) {
17             to_left[layer][i] = 0;
18         } else {
19             to_left[layer][i] = to_left[layer][i - 1];
20         }
21         if(val[layer][i] < sorted[mid]) {
22             ++to_left[layer][i];
23             val[layer + 1][rec_l++] = val[layer][i];
24         } else if(val[layer][i] > sorted[mid]) {
25             val[layer + 1][rec_r++] = val[layer][i];
26         } else {
27             if(suppose != 0) {
28                 --suppose;
29                 ++to_left[layer][i];
30                 val[layer + 1][rec_l++] = val[layer][i];
31             } else {
32                 val[layer + 1][rec_r++] = val[layer][i];
33             }
34         }
35     }
36     build_tree(l, mid, layer + 1);
37     build_tree(mid + 1, r, layer + 1);
38 }
39 
40 int query(int l, int r, int layer, int ql, int qr, int kth) {
41     if(l == r) return val[layer][l];
42     int s, ss;
43     if(l == ql) {
44         s = 0;
45         ss = to_left[layer][qr];
46     } else {
47         s = to_left[layer][ql - 1];
48         ss = to_left[layer][qr] - s;
49     }
50     int mid = (l + r) >> 1;
51     if(kth <= ss) {
52         return query(l, mid, layer + 1, l + s, l + s + ss - 1, kth);
53     }
54     return query(mid + 1, r, layer + 1, mid + 1 + ql - s - l, mid + 1 + qr - l - s - ss, kth - ss);
55 }
56 
57 int main() {
58 #ifndef ONLINE_JUDGE
59     freopen("data.in", "r", stdin); freopen("data.out", "w", stdout);
60 #endif
61     scanf("%d%d", &n, &m);
62     for(int i = 1; i <= n; ++i) {
63         scanf("%d", &sorted[i]);
64         val[0][i] = sorted[i];
65     }
66     sort(sorted + 1, sorted + n + 1);
67     build_tree(1, n, 0);
68     while(m--) {
69         int l, r, k;
70         scanf("%d%d%d", &l, &r, &k);
71         printf("%d\n", query(1, n, 0, l, r, k));
72     }
73     return 0;
74 }