ST表

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <cstring>
 5 #include <cmath>
 6 #define REP(i, s, n) for(int i = s; i <= n; i ++)
 7 using namespace std;
 8 const int maxn = 100000 + 10;
 9 int Log[maxn], A[maxn], d[maxn][20], n, Q;
10 void RMQ(){
11     Log[0] = -1;
12     REP(i, 1, n) d[i][0] = A[i], Log[i] = Log[i >> 1] + 1;
13     for(int j = 1; (1 << j) <= n; j ++)
14         for(int i = 1; i + (1 << j) - 1 <= n; i ++)
15             d[i][j] = max(d[i][j - 1], d[i + (1 << (j - 1))][j - 1]);
16     return ;
17 }
18 int query(int L, int R){
19     int k = Log[R - L + 1]; return max(d[L][k], d[R - (1 << k) + 1][k]);
20 }
21 void read(int &x){
22     x = 0; int sig = 1; char ch = getchar();
23     while(!isdigit(ch)) { if(ch == ‘-‘) sig = -1; ch = getchar(); }
24     while(isdigit(ch)) x = 10 * x + ch - ‘0‘, ch = getchar();
25     x *= sig; return ;
26 }
27 void init(){
28     read(n); read(Q);
29     REP(i, 1, n) read(A[i]);
30     RMQ();
31     return ;
32 }
33 void work(){
34     int L, R;
35     while(Q --){
36         read(L); read(R);
37         printf("%d\n", query(L, R));
38     }
39     return ;
40 }
41 void print(){
42 
43     return ;
44 }
45 int main(){
46     init();
47     work();
48     print();
49     return 0;
50 }