51Nod 1174 区间中最大的数(RMQ)

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;
const int maxn = 10000 + 5;
int a[maxn];
int f[maxn][15];

void rmq(int cnt){
    memset(f, 0, sizeof(f));
    for (int i = 1; i <= cnt; i++){
        f[i][0] = a[i];
    }

    //O(nlogn)
    for (int j = 1; j < 15; j++){
        for (int i = 1; i <= cnt; i++){
            if (i + (1 << j) - 1 <= cnt){
                f[i][j] = max(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
            }
        }
    }
}


int Query(int x, int y){
    int k = 0;
    while ((1 << (k + 1)) <= y - x + 1)
        k++;      
    return max(f[x][k], f[y - (1 << k) + 1][k]);
}

int main(){
    ios::sync_with_stdio(false);

    int n;
    cin >> n;
    for (int i = 1; i <= n; i++){
        cin >> a[i];
    }
    rmq(n);
    int m;
    cin >> m;
    while (m--){
        int x, y;
        cin >> x >> y;
        x++, y++;
        int ans = Query(x, y);
        cout << ans << endl;
    }

    //system("pause");
    return 0;
}