萌新线段树只有9分(A了第一个点)，看了看之前的讨论也没有发现类似的错误

#include<cstdio>
#include<cstring>
#include<algorithm>
#define int long long
using namespace std;
int n,m,sum,cnt;
int num[100100];
struct node{
	int l,r,sum,lm,rm,maxn;
}tree[4000100];
void pushup(int id)
{
	if(tree[id*2].rm<0&&tree[id*2+1].lm<0)tree[id].maxn=(tree[id*2].rm,tree[id*2+1].lm);
	else
	{
		tree[id].maxn=0;
		if(tree[id*2].rm>0)tree[id].maxn+=tree[id*2].rm;
		if(tree[id*2+1].lm>0)tree[id].maxn+=tree[id*2+1].lm;
	}
	tree[id].maxn=max(tree[id].maxn,max(tree[id*2].maxn,tree[id*2+1].maxn));	
	tree[id].lm=max(tree[id*2].lm,tree[id*2].sum+tree[id*2+1].lm);
	tree[id].rm=max(tree[id*2+1].rm,tree[id*2].rm+tree[id*2+1].sum);
	tree[id].sum=tree[id*2].sum+tree[id*2+1].sum;	
}
void build(int id,int l,int r)
{
	tree[id].l=l;tree[id].r=r;tree[id].maxn=0;
	if(l==r)
	{
		tree[id].lm=tree[id].rm=tree[id].maxn=tree[id].sum=num[l];
		return;
	}
	int mid=(l+r)/2;
	build(id*2,l,mid);
	build(id*2+1,mid+1,r);
	pushup(id);
}
void add(int id,int p,int k)
{
	if(tree[id].l==tree[id].r&&tree[id].l==p)
	{
		tree[id].lm=tree[id].rm=tree[id].maxn=tree[id].sum=k;
		return;
	}
	int mid=(tree[id].l+tree[id].r)/2;
	if(p<=mid)add(id*2,p,k);
	if(p>mid)add(id*2+1,p,k);
	pushup(id);
}
int find(int id,int l,int r)
{
	if(l<=tree[id].l&&tree[id].r<=r)return tree[id].maxn;
	int mid=(tree[id].l+tree[id].r)/2;
	int ans=-0x3f3f3f3f;
	if(l<=mid)ans=max(ans,find(id*2,l,r));
	if(r>mid)ans=max(ans,find(id*2+1,l,r));
	return ans;
}
signed main()
{
	scanf("%lld%lld",&n,&m);
	for(int i=1;i<=n;++i)scanf("%lld",&num[i]);
	build(1,1,n);
	for(int i=1;i<=m;++i)
	{
		int x,y,z;
		scanf("%lld",&z);
		if(z==1)
		{
			scanf("%lld%lld",&x,&y);
			if(x>y)swap(x,y);
			printf("%lld\n",find(1,x,y));
		}
		else
		{
			scanf("%lld%lld",&x,&y);
			add(1,x,y);
		}
	}
	return 0;
}