st表

st表

#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
const int N = 2e5 + 10, M = 18;
int f[N][M], a[N];
int 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()
{
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    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;
}

类模板

template<typename T> struct ST
{
    ST(T a[], int n){
        siz = n;
        maxv.resize(n+1); minv.resize(n+1);
        int t = __lg(n) + 1;
        for(int i=1;i<=n;i++) maxv[i].resize(t), minv[i].resize(t);
        
        for(int i = 1; i <= n; i++) maxv[i][0] = minv[i][0] = a[i];
        for(int j = 1; j < t; j++) 
        {
            for(int i = 1; i <= n - (1<<j)+1; i++)
            {
                maxv[i][j] = max(maxv[i][j-1], maxv[i+(1 << (j-1))][j-1]);
                minv[i][j] = min(minv[i][j-1], minv[i+(1 << (j-1))][j-1]);
            }
        }
    }
    T getmax(int l,int r)
	{
	    int k = __lg(r-l+1);
	    return max(maxv[l][k],maxv[r-(1<<k)+1][k]);
    }    
    T getmin(int l,int r)
	{
	    int k = __lg(r-l+1);
	    return min(minv[l][k],minv[r-(1<<k)+1][k]);
    }    
private:
    int siz = 0;
    vector<vector<T>> maxv, minv;
};