蓝桥杯-操作格子(线段树)

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<cmath>
#define ll __int64
#define INF 0x3fffffff
using namespace std;

struct Node
{
    int l,r;
    int Max,Sum;
    int Mid(){
        return (l+r)/2;
    }
}tree[400000];

void BuildTree(int root,int l,int r)
{
    tree[root].Max=-INF;
    tree[root].Sum=0;
    tree[root].l=l;
    tree[root].r=r;
    if(l!=r)
    {
        BuildTree(2*root+1,l,(l+r)/2);
        BuildTree(2*root+2,(l+r)/2+1,r);
    }
}

void Insert(int root,int i,int v)
{
    if(tree[root].l==tree[root].r)
    {
        tree[root].Max=tree[root].Sum=v;
        return;
    }
    if(i<=tree[root].Mid())
    {
        Insert(2*root+1,i,v);
    }
    else
    {
        Insert(2*root+2,i,v);
    }
    tree[root].Max=max(tree[2*root+1].Max,tree[2*root+2].Max);
    tree[root].Sum=tree[2*root+1].Sum+tree[2*root+2].Sum;
}

int QuerySum(int root,int l,int r)
{
    if(tree[root].l==l&&tree[root].r==r){
        return tree[root].Sum;
    }
    if(r<=tree[root].Mid()){
        return QuerySum(2*root+1,l,r);
    }else if(l>tree[root].Mid()){
        return QuerySum(2*root+2,l,r);
    }else{
        return QuerySum(2*root+1,l,tree[root].Mid())+QuerySum(2*root+2,tree[root].Mid()+1,r);
    }
}

int QueryMax(int root,int l,int r)
{
    if(tree[root].l==l&&tree[root].r==r){
        return tree[root].Max;
    }
    if(r<=tree[root].Mid()){
        return QueryMax(2*root+1,l,r);
    }else if(l>tree[root].Mid()){
        return QueryMax(2*root+2,l,r);
    }else{
        return max(QueryMax(2*root+1,l,tree[root].Mid()),QueryMax(2*root+2,tree[root].Mid()+1,r));
    }
}

int main()
{
    //freopen("d:\\Test.txt","r",stdin);
	int n,m;
	cin>>n>>m;
	BuildTree(0,1,n);
	for(int i=1;i<=n;i++)
	{
	    int value;
	    cin>>value;
	    Insert(0,i,value);
	}
	for(int i=0;i<m;i++)
	{
	    int p,x,y;
	    cin>>p>>x>>y;
	    if(p==1){
	        Insert(0,x,y);
	    }else if(p==2){
	        cout<<QuerySum(0,x,y)<<endl;
	    }else if(p==3){
	        cout<<QueryMax(0,x,y)<<endl;
	    }
	}
	return 0;
}