【hihoCoder第十六周】RMQ-ST算法

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 vector<int> A;
 5 int dp[1000005][20];
 6 
 7 void RMQ_init () {
 8     int n = A.size();
 9     for (int i = 0; i < n; ++ i) {
10         dp[i][0] = A[i];
11     }
12     for (int j = 1; (1 << j) <= n; ++ j) {
13         for (int i = 0; i + (1 << j) - 1 < n; ++ i) {
14             dp[i][j] = min(dp[i][j - 1], dp[i + (1 << (j - 1))][j - 1]);
15         }
16     }
17 }
18 
19 int RMQ (int L, int R) {
20     int k = 0;
21     while ((1 << (k + 1)) <= R - L + 1) ++ k;
22     return min(dp[L][k], dp[R - (1 << k) + 1][k]);
23 }
24 
25 int main () {
26     int n;
27     while (~scanf ("%d", &n)) {
28         int x, op_n;
29         for (int i = 0 ; i < n; ++ i) {
30             scanf ("%d", &x);
31             A.push_back(x);
32         }
33         /*
34         for (int i = 0; i < A.size() - 1; ++ i) {
35             cout << A[i] << endl;
36         }
37         */
38         RMQ_init ();
39         int a, b;
40         scanf ("%d", &op_n);
41         for (int i = 0; i < op_n; ++ i) {
42             scanf ("%d%d", &a, &b);
43             printf ("%d\n", RMQ(a - 1, b - 1));
44         }
45     }
46     return 0;
47 }