题解 | 中位数

def check(a,n,m,x):
    pre=[0]*(1+n)
    for i in range(1,n+1):
        pre[i]=pre[i-1]+(1 if a[i-1]>=x else -1)
    pre_l=pre[0]
    for r in range(1,n+1):
        if r >=m:
            pre_l=min(pre_l,pre[r-m])
            if pre[r]-pre_l>0:
                return True
    return False
T=int(input())
for i in range(T):
    n,m=map(int,input().split())
    a=list(map(int,input().split()))
    l,r=0,10**9
    while l<r:
        mid=(l+r+1)//2
        if check(a,n,m,mid):
            l=mid
        else:
            r=mid-1
    print(l)