SPOJ GSS3 Can you answer these queries III ——线段树

#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>

#include <map>
#include <set>
#include <queue>
#include <string>
#include <iostream>
#include <algorithm>

using namespace std;

#define maxn 2000005
#define eps 1e-8
#define db double
#define ll long long
#define inf 0x3f3f3f3f
#define F(i,j,k) for (ll i=j;i<=k;++i)
#define D(i,j,k) for (ll i=j;i>=k;--i)

void Finout()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
//    freopen("wa.txt","w",stdout);
    #endif
}

ll Getll()
{
    ll x=0,f=1; char ch=getchar();
    while (ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) f=-1; ch=getchar();}
    while (ch>=‘0‘&&ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
    return x*f;
}

ll buf=100005,next[maxn],pos[maxn];

struct Node{
	ll lx,rx,mx,sum;
	Node operator + (Node x)
	{
		Node ret;
		ret.lx=max(lx,sum+x.lx);
		ret.rx=max(x.sum+rx,x.rx);
		ret.sum=sum+x.sum;
		ret.mx=max(max(mx,x.mx),max(rx+x.lx,max(ret.lx,ret.rx)));
		return ret;
	}
}t[maxn];

ll n,a[maxn],q,L,R,x,c;

struct Problem{ll l,r,id,ans;}p[maxn];

bool cmp1(Problem x,Problem y)
{return x.l==y.l?x.r<y.r:x.l<y.l;}
bool cmp2(Problem x,Problem y)
{return x.id<y.id;}

void Build(ll o,ll l,ll r)
{
	if (l==r)
	{
		t[o].lx=t[o].rx=t[o].mx=t[o].sum=a[l];
		return ;
	}
	ll mid=l+r>>1;
	Build(o<<1,l,mid);
	Build(o<<1|1,mid+1,r);
	t[o]=t[o<<1]+t[o<<1|1];
}

Node Query(ll o,ll l,ll r)
{
	if (L<=l&&r<=R) return t[o];
	ll mid=l+r>>1;
	if (L>mid) return Query(o<<1|1,mid+1,r);
	else if (R<=mid) return Query(o<<1,l,mid);
	else return Query(o<<1,l,mid)+Query(o<<1|1,mid+1,r);
}

void Modify(ll o,ll l,ll r)
{
	if (l==r)
	{
		t[o].lx=t[o].rx=t[o].mx=t[o].sum=c;
		return ;
	}
	ll mid=l+r>>1;
	if (x<=mid) Modify(o<<1,l,mid);
	else Modify(o<<1|1,mid+1,r);
	t[o]=t[o<<1]+t[o<<1|1];
	 
}

int main()
{
	Finout(); n=Getll();
//	printf("%lld\n",n);
	F(i,1,n) a[i]=Getll();
//	F(i,1,n) printf("%lld ",a[i]);
//	printf("\n");
	Build(1,1,n); q=Getll();
	F(i,1,q)
	{
		ll opt=Getll();
		switch (opt)
		{
			case 1:
				L=Getll();
				R=Getll();
				printf("%lld\n",Query(1,1,n).mx);
			break;
			case 0:
				x=Getll();
				c=Getll();
				Modify(1,1,n);
			break;
		}
	}
}