单调队列

luogu P1886 滑动窗口 https://www.luogu.org/problemnew/show/P1886

// luogu-judger-enable-o2
#include<bits/stdc++.h>
using namespace std;
#define il inline
#define rg register
typedef long long ll;
#define max(a,b) (a)<(b)?(b):(a)
#define gmax(a,b) a=max(a,b)
#define min(a,b) (a)<(b)?(a):(b)
#define gmin(a,b) a=min(a,b)
#define FOR(i,a,b) for(rg int i=a;i<=b;++i)
#define For(i,a,b) for(rg int i=a;i>=b;--i)
#define gc pa==pb&&(pb=(pa=buf)+fread(buf,1,100000,stdin),pa==pb)?EOF:*pa++
static char buf[100000],*pa(buf),*pb(buf);
il int rd(){
    rg int x(0),w(1);
    rg char c(gc);
    while(c<'0'||c>'9')
    {
        if(c=='-') w=-1;
        c=gc;
    }
    while(c>='0'&&c<='9') x=x*10+c-48,c=gc;
    return x*w;}
const int N=1e6+5;
int q[N],hd,tl;
int n,k,a[N],ans;

int main()
{
    n=rd(),k=rd();
    FOR(i,1,n) a[i]=rd();
    hd=tl=1;ans=1e9;
    FOR(i,1,k-1) 
    {
        while(hd<=tl && a[q[tl]]>=a[i]) --tl;
        q[++tl]=i;
    }
    FOR(i,k,n)
    {
        while(hd<=tl && q[hd]<=i-k) ++hd;
        while(hd<=tl && a[q[tl]]>=a[i]) --tl;
        q[++tl]=i;
        printf("%d ",a[q[hd]]);
    }
    printf("
");
    hd=tl=1;ans=-(1e9);
    FOR(i,1,k-1)
    {
        while(hd<=tl && a[q[tl]]<=a[i]) --tl;
        q[++tl]=i;
    }
    FOR(i,k,n)
    {
        while(hd<=tl && q[hd]<=i-k) ++hd;
        while(hd<=tl && a[q[tl]]<=a[i]) --tl;
        q[++tl]=i;
        printf("%d ",a[q[hd]]);
    }
    return 0;
}