51nod 1174 1174 区间中最大的数

Posted 2020-08-17 GraceSkyer

题目链接：51nod 1174 1174 区间中最大的数

ST（Sparse Table）算法学习参考博客：http://blog.csdn.net/niushuai666/article/details/6624672

O(nlogn)预处理，O(1)查询

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cmath>
 4 using namespace std;
 5 const int N = 10001;
 6 int ma[N][20];
 7 int a[N];
 8 int n;
 9 void RMQ_init(){
10     int i, j;
11     for(i = 0; i < n; ++i) ma[i][0] = a[i];
12     int m = (int)(log(n*1.0) / log(2.0));
13     for(i = 1; i <= m; ++i){
14         for(j = 0; j < n; ++j){
15             ma[j][i] = ma[j][i-1];
16             if(j + (1 << (i-1)) <= n)
17                 ma[j][i] = max(ma[j][i], ma[j + (1 << (i-1))][i-1]);
18         }
19     }
20 }
21 int RMQ_max(int l, int r){
22     int m = (int)(log((r-l+1)*1.0) / log(2.0));
23     return max(ma[l][m], ma[r - (1 << m) + 1][m]);
24 }
25 int main(){
26     int q, i;
27     scanf("%d", &n);
28     for(i = 0; i < n; ++i) scanf("%d", &a[i]);
29     RMQ_init();
30     scanf("%d", &q);
31     int l, r;
32     while(q--){
33         scanf("%d%d", &l, &r);
34         printf("%d\\n", RMQ_max(l, r));
35     }
36     return 0;
37 }

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