剑指offer python版 丑数 (只含有2，3，5因子)

def aa(n):
    ugly=[1]
    t2,t3,t5=0,0,0
    while n>1:
        while ugly[t2]*2 <=ugly[-1]:
            t2+=1
        while ugly[t3]*3 <=ugly[-1]:
            t3 +=1
        while ugly[t5]*5<=ugly[-1]:
            t5 +=1
            
        ugly.append(min(ugly[t2]*2,ugly[t3]*3,ugly[t5]*5))
        n-=1
    return ugly


print(aa(18))