坑人的从0开始

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5;
typedef long long ll;
int a[N];
struct Node{
    int l,r;
    int data;
    
}tree[4*N];
//p: 当前节点的编号  l 表示节点负责的范围的左区间
void build(int p ,int l,int r)
{
    tree[p].l = l;
    tree[p].r = r;
    if(l == r)
    {
        tree[p].data = a[l];
        return;
    }
    int mid = (l+r)>>1;
    build(p*2+1,l,mid );
    build(p*2+2 ,mid + 1,r);
    tree[p].data = tree[p*2+1].data + tree[p*2+2].data;
}

ll query(int p,int x,int y)
{
    if(tree[p].l>=x && tree[p].r <= y)
    {
        return tree[p].data;
    }
    ll res = 0;
    int mid = (tree[p].l +  tree[p].r)>>1;
    if( x <=mid ) res += query(p*2+1  ,x,y);
    if (y>mid ) res += query(p*2+2,x,y);
    return res;
    
}

void update(int p,int x,int v)
{
    if(tree[p].l == tree[p].r)
    {
        tree[p].data = v;

        return;
    }
    int mid = (tree[p].l +   tree[p].r)>>1;
    if(x <= mid) update(p*2+1,x,v);
    else update(p*2+2, x,v);
    tree[p].data = tree[p*2+1].data + tree[p*2+2].data;
}

int main(){
	int n,q ;
	cin>>n>>q ;
	for(int i = 0;i<n;i++)cin>>a[i];
	build(0,0,n-1);
	while(q--)
	{
	    int x,y,z;
	    cin>>x>>y>>z;
	    if(x == 1)
	    {
	        update(0,y,z);
	    }
	    else if(x == 2)
	    {
	      
        	cout<<query(0,y,z)<<endl;
	        
	    }
	    
	}



	

}