北大zhw大神bzoj1756代码

#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
int tree[1048576][7],a[600005],n,m,A,B,C,i,ans,t,x;
void Update(int x)
{
    tree[x][2]=tree[x*2][2]+tree[x*2+1][2];
    tree[x][3]=max(tree[x*2][3],tree[x*2+1][3]);
    tree[x][4]=max(tree[x*2][4],tree[x*2][2]+tree[x*2+1][4]);
    tree[x][5]=max(tree[x*2+1][5],tree[x*2+1][2]+tree[x*2][5]);
    tree[x][6]=max(max(tree[x*2][6],tree[x*2+1][6]),tree[x*2][5]+tree[x*2+1][4]);
}
int WORK(int root,int l,int r)
{
    if (tree[root][0]==l && tree[root][1]==r) return tree[root][3];
    int mid=(tree[root][0]+tree[root][1])/2,p=-2000000000,q=-2000000000;
    if (l<=mid) p=WORK(root*2,l,min(mid,r));
    if (r>mid) q=WORK(root*2+1,max(l,mid+1),r);
    return max(p,q);
}
void work(int root,int l,int r)
{
    if (tree[root][0]==l && tree[root][1]==r)
    {
        ans=max(ans,tree[root][4]+t);
        ans=max(ans,tree[root][6]);
        t=max(t+tree[root][2],tree[root][5]);
        t=max(t,0);
        return;
    }
    int mid=(tree[root][0]+tree[root][1])/2;
    if (l<=mid) work(root*2,l,min(mid,r));
    if (r>mid) work(root*2+1,max(mid+1,l),r);
}
int main()
{
    scanf("%d%d",&n,&m);
    for (i=1; i<=n; i++) scanf("%d",&a[i]);
    for (i=524288; i<=1048575; i++)
    {
        tree[i][0]=tree[i][1]=i;
        tree[i][2]=tree[i][3]=a[i-524287];
        tree[i][4]=tree[i][5]=tree[i][6]=max(a[i-524287],0);
    }
    for (i=524287; i>=1; i--)
    {
        tree[i][0]=tree[i*2][0];
        tree[i][1]=tree[i*2+1][1];
        Update(i);
    }
    for (i=1; i<=m; i++)
    {
        scanf("%d%d%d",&A,&B,&C);
        if (A==2)
        {
            x=524287+B;
            tree[x][2]=tree[x][3]=C;
            tree[x][4]=tree[x][5]=tree[x][6]=max(C,0);
            while (x!=1)
            {
                x/=2;
                Update(x);
            }
        }
        else
        {
            if (B>C) swap(B,C);
            t=0;
            ans=WORK(1,B+524287,C+524287);
            if (ans<0) printf("%d\n",ans); else
            {
                work(1,B+524287,C+524287);
                printf("%d\n",ans);
            }
        }
    }
    return 0;
}