Python 代码

N = 50010
h, e, ne = [-1] * N, [0] * (2*N), [0] * (2*N) 
idx = 0
max_step = 0

def add(a, b):
    global idx
    e[idx] = b
    h[a], ne[idx] = idx, h[a]
    idx += 1

def div(x):
    res = 1
    for i in range(2, int(x**0.5) + 1):
        if x % i == 0:
            res += i
            if x // i != i:
                res += x // i
    return res

def dfs(cur):
    global max_step
    nn = h[cur]
    ret1, ret2 = 0, 0
    while nn != -1:
        son = e[nn]
        tmp = dfs(son) + 1
        if tmp >= ret1: ret1, ret2 = tmp, ret1
        elif tmp > ret2: ret2 = tmp
        nn = ne[nn]
    max_step = max(max_step, ret1 + ret2)
    return ret1

n = int(input())
for a in range(1, n+1):
    b = div(a)
    if b < a:
        add(b, a)

dfs(1)