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| #include<bits/stdc++.h>
using namespace std;
const int maxn= 200005;
const int INF=0x3fffffff;
int Max[maxn<<2],Min[maxn<<2];
struct node{
int l,r;
friend bool operator <(const node &a,const node &b)
{
return a.l<b.l;
}
}a[maxn];
bool cmp(node a,node b)
{
return a.l<b.l;
}
void build(int p,int l,int r)
{
if(l==r)
{
Max[p]=a[l].l+a[l].r;
Min[p]=a[l].r-a[l].l;
return ;
}
int mid=(l+r)/2;
build(p*2,l,mid);
build(p*2+1,mid+1,r);
Max[p]=max(Max[p*2],Max[p*2+1]);
Min[p]=min(Min[p*2],Min[p*2+1]);
}
int Quary_Max(int l,int r,int p,int x,int y)
{
if(l>y||r<x)return 0;
if(l>=x&&r<=y)return Max[p];
int mid=(l+r)>>1;
return max(Quary_Max(l,mid,p*2,x,y),Quary_Max(mid+1,r,p*2+1,x,y));
}
int Quary_Min(int l,int r,int root,int x,int y)
{
if(l>y||r<x)return INF;
if(l>=x&&r<=y)return Min[root];
int mid=(l+r)>>1;
return min(Quary_Min(l,mid,root*2,x,y),Quary_Min(mid+1,r,root*2+1,x,y));
}
int main()
{
int n;
scanf("%d",&n);
for(int i=1;i<=n;i++)scanf("%d%d",&a[i].l,&a[i].r);
sort(a+1,a+1+n,cmp);
build(1,1,n);
int ans=0;
node tmp;
tmp.r=0;
int l,r;
for(int i=1;i<=n;i++)
{
tmp.l=a[i].l;
l=lower_bound(a+1,a+1+n,tmp)-a;
tmp.l=a[i].r;
r=upper_bound(a+1,a+1+n,tmp)-a-1;
if(l>r)continue;
ans=max(ans,Quary_Max(1,n,1,l,r)-a[i].r-a[i].l);
ans=max(ans,a[i].r-a[i].l-Quary_Min(1,n,1,l,r));
}
printf("%d\n",ans);
return 0;
}
|