1273. 天才的记忆 题解

#include <bits/stdc++.h>
using namespace std;
const int N = 200010, M = 18;

int n, m;
int a[N], f[N][M];

void init()
{
    for (int j = 0; j < M; j++)
        for (int i = 1; i + (1 << j) - 1 <= n; i++)
            if (!j) f[i][j] = a[i];
            else f[i][j] = max(f[i][j - 1], f[i + (1 << j - 1)][j - 1]);
}

int query(int l, int r)
{
    int len = r - l + 1;
    int k = log(len) / log(2);
    return max(f[l][k], f[r - (1 << k) + 1][k]);
}

int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)    cin >> a[i];
    
    init();
    
    cin >> m;
    while (m--)
    {
        int l, r;
        cin >> l >> r;
        cout << query(l, r) << endl;
    }
    return 0;
}