单调队列写法：

#include<iostream>
#include<stack>
#include<string>
#include<cmath>
#include<iomanip>
#include<algorithm>
#include<climits>
#include<cstdio>
using namespace std;
int n, m, a[2000002], q[2000002], h, t;
int main()
{
	scanf("%d%d", &n, &m);
	h = t = q[1] = 1;
	scanf("%d", &a[1]);
	printf("0\n");
	for (int i = 2; i <= n; ++i)
	{
		scanf("%d", &a[i]);
		if (q[h] + m < i)++h;
		while (h <= t && a[i - 1] <= a[q[t]])--t;
		q[++t] = i - 1;
		printf("%d\n", a[q[h]]);
	}
	return 0;
}

while循环那行本来写的是while (h <= t && a[i - 1] < a[q[t]])--t;，结果改成<=就对了，不过我觉得这应该不会影响什么。但是为什么会过呢？