洛谷P3865_树状数组

#include <bits/stdc++.h>
/*
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
*/
using namespace std;

const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;

#define f(i, a, b) for (int i = a; i <= b; i++)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define lowbit(x) (x&(-x))

#define fi first
#define se second
#define SZ(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))

typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;

using ll=long long;

ll n,m,a[(int)1e5+9];

struct BIT
{
    ll  h[(int)1e5 + 9];
    void update(int x,int k)
    {
        while(x<=n){
            h[x]=k;
            int low=lowbit(x);
            for(int i=1;i<low;i<<=1)h[x]=max(h[x],h[x-i]);
            x+=lowbit(x);
        }  
    }
    ll gmin(int l, int r)
    {
        ll ans = 0;
        while (r >= l)
        {
            ans = max(ans, a[r]);
            r--;
            while (r - lowbit(r) >= l)
            {
                ans = max(h[r], ans);
                r -= lowbit(r);
            }
        }
        return ans;
    }
}b;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>m;
    f(i,1,n){
        cin>>a[i];
    }
    f(i,1,n)b.update(i,a[i]);
    for(int i=1,x,y;i<=m;++i){
        cin>>x>>y;
        cout<<b.gmin(x,y)<<"\n";
    }
    return 0;
}