Dynamic maximum sub-segments and

#include <bits/stdc++.h>using namespace Std;const int Maxn=5e5+10;inline int read () {int X=0,f=1;char ch; Do{ch=getchar (); if (ch== '-') f=-1;}    while (!isdigit (CH)); do{x=x*10+ch-' 0 '; Ch=getchar ();}    while (IsDigit (CH)); return f*x;}    int n,m,a[maxn];struct node{#define Lson t[k].lc #define Rson t[k].rc int LC,RC; int Sum,lmax,rmax,dat;}    T[maxn<<1];int tot=1;inline void pushup (int k) {t[k].sum=t[lson].sum+t[rson].sum;    T[k].lmax=max (T[lson].lmax,t[lson].sum+t[rson].lmax);    T[k].rmax=max (T[rson].rmax,t[rson].sum+t[lson].rmax); T[k].dat=max (Max (T[lson].dat,t[rson].dat), T[lson].rmax+t[rson].lmax);}        void build (int k,int l,int R) {if (l==r) {t[k].sum=t[k].lmax=t[k].rmax=t[k].dat=a[l];    Return    } int mid=l+r>>1;    Lson=++tot,build (Lson,l,mid);    Rson=++tot,build (RSON,MID+1,R); Pushup (k);}        void Modify (int k,int l,int r,int pos,int val) {if (l==r) {t[k].sum=t[k].lmax=t[k].rmax=t[k].dat=val;    Return } int mid=l+r>>1;    if (pos<=mid) modify (Lson,l,mid,pos,val);    else modify (Rson,mid+1,r,pos,val); Pushup (k);}    node query (int k,int l,int r,int x,int y) {if (l==x&&r==y) return t[k];    int mid=l+r>>1;    if (y<=mid) return query (lson,l,mid,x,y);    else if (x>mid) return query (rson,mid+1,r,x,y);        else{node Ls=query (lson,l,mid,x,mid);        Node Rs=query (rson,mid+1,r,mid+1,y);        node res;        Res.sum=ls.sum+rs.sum;        Res.lmax=max (Ls.lmax,ls.sum+rs.lmax);        Res.rmax=max (Rs.rmax,rs.sum+ls.rmax);        Res.dat=max (Max (Ls.dat,rs.dat), Ls.rmax+rs.lmax);    return res;    }}void Read_and_parse () {n=read (), M=read ();    for (int i=1;i<=n;i++) a[i]=read (); Build (1,1,n);}        void Solve () {while (m--) {int k=read (), X=read (), Y=read ();            if (k==1) {if (x>y) swap (x, y);        printf ("%d\n", Query (1,1,n,x,y). dat);    }else Modify (1,1,n,x,y);    }}int Main () {read_and_parse ();    Solve (); return 0;}

Dynamic maximum child segments and