單調佇列

划水

用兩個指標推，單調佇列維護最大最小值。

程式碼：

#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 3000005
#define F inline
using namespace std;
int n,k,ans,a[N],mn[N],mx[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; char ch=readc();
	while (!isdigit(ch)) ch=readc();
	while (isdigit(ch)) x=(x<<3)+(x<<1)+(ch^48),ch=readc();
	return x;
}
int main(){
	k=_read(),n=_read();
	for (int i=1;i<=n;i++) a[i]=_read();
	int ln=1,rn=0,lx=1,rx=0,l=1,r=0;
	while (r<
 
n){
		int x=a[++r];
		while (ln<=rn&&a[mn[rn]]>=x) rn--;
		while (lx<=rx&&a[mx[rx]]<=x) rx--;
		mn[++rn]=mx[++rx]=r;
		while (a[mx[lx]]-a[mn[ln]]>k&&ln<=rn&&lx<=rx){
			l++; if (mn[ln]<l) ln++; if (mx[lx]<l) lx++;
		}
		ans=max(ans,r-l+1);
	}
 

	return printf("%d\n",ans),0;
}