RMQ st算法 区间最值模板

#include<bits/stdc++.h>

const int N=1e6+5;
const int Logn=20;

int f[N][Logn],a[N],lg[N],n,m;

int main(){
    cin>>n>>m;
    rep(i,1,n) cin>>a[i];
    lg[0]=-1;
    rep(i,1,n) fa[i][0]=a[i],lg[i]=lg[i>>1]+1;
    
    rep(j,1,Logn)
    for(int i=1;i+(1<<j)-1<=n;i++)
    f[i][j]=max(f[i][j-1],f[i+(1<<j-1)][j-1]);
    
    while(m--){
        int x,y;cin>>x>>y;
        int k=lg[y-x+1];
        printf("%d\n",max(f[x][k],f[y-(1<<k)+1][k]));}
    return 0;
}