單調隊列
單調隊列維護最低溫度遞減的序列,同時保證隊頭的最低溫度低於隊尾的最高溫度就好了。
代碼:
#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 1000005
#define F inline
using namespace std;
int n,l,r,ans,a[N],b[N],q[N];
F char readc(){
static char buf[100000],*l=buf,*r=buf;
if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
return l==r?EOF:*l++;
}
F int _read(){
int x=0,f=1; char ch=readc();
while (!isdigit(ch)){ if (ch=='-') f=-1; ch=readc(); }
while (isdigit(ch)) x=(x<<3)+(x<<1)+(ch^48),ch=readc();
return x*f;
}
int main(){
n=_read(),l=ans=1;
for (int i=1,lst;i<=n;i++){
a[i]=_read(),b[i]=_read();
while (l<=r&&a[q[l]]>b[i]) l++; lst=i;
while (l<=r&&a[i]>a[q[r]]) lst=q[r--];
a[lst]=a[i],q[++r]=lst,ans=max(ans,i-q[l]+1);
}
return printf("%d",ans),0;
}