[luoguP1816] 忠诚（RMQ || 线段树）

 1 #include <cstdio>
 2 #define N 100001
 3 #define min(x, y) ((x) < (y) ? (x) : (y))
 4 
 5 int n, m;
 6 int a[N], d[N][21];
 7 
 8 int main()
 9 {
10     int i, j, k, x, y;
11     scanf("%d %d", &n, &m);
12     for(i = 1; i <= n; i++) scanf("%d", &a[i]);
13     for(i = 1; i <= n; i++) d[i][0] = a[i];
14     for(j = 1; (1 << j) <= n; j++)
15         for(i = 1; i + (1 << j) - 1 <= n; i++)
16             d[i][j] = min(d[i][j - 1], d[i + (1 << (j - 1))][j - 1]);
17     for(i = 1; i <= m; i++)
18     {
19         scanf("%d %d", &x, &y);
20         k = 0;
21         while((1 << (k + 1)) <= y - x + 1) k++;
22         printf("%d ", min(d[x][k], d[y - (1 << k) + 1][k]));
23     }
24     return 0;
25 }