51nod 1174 1174 区间中最大的数

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

#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
const int N = 10001;
int ma[N][20];
int a[N];
int n;
void RMQ_init(){
    int i, j;
    for(i = 0; i < n; ++i) ma[i][0] = a[i];
    int m = (int)(log(n*1.0) / log(2.0));
    for(i = 1; i <= m; ++i){
        for(j = 0; j < n; ++j){
            ma[j][i] = ma[j][i-1];
            if(j + (1 << (i-1)) <= n)
                ma[j][i] = max(ma[j][i], ma[j + (1 << (i-1))][i-1]);
        }
    }
}
int RMQ_max(int l, int r){
    int m = (int)(log((r-l+1)*1.0) / log(2.0));
    return max(ma[l][m], ma[r - (1 << m) + 1][m]);
}
int main(){
    int q, i;
    scanf("%d", &n);
    for(i = 0; i < n; ++i) scanf("%d", &a[i]);
    RMQ_init();
    scanf("%d", &q);
    int l, r;
    while(q--){
        scanf("%d%d", &l, &r);
        printf("%d\n", RMQ_max(l, r));
    }
    return 0;
}