单调队列（数组优化？)P1886

class Deque{
public:
    int a[maxn];
    int pl=1,pr=0;
}Deq;
int a[maxn];
int n,k;
void solve(){
    Deq.pl=1;Deq.pr=0;
    for(int i=1;i<=n;i++){
        while(Deq.pr>=Deq.pl&&a[Deq.a[Deq.pr]]<a[i])Deq.pr--;//弹尾
        Deq.a[++Deq.pr]=i;//入尾
        if(Deq.a[Deq.pl]+k<=i)Deq.pl++;//弹首
        o(a[Deq.a[Deq.pl]]);putchar(' ');
    }
    putchar('
');
}