剑指Offer 49 丑数

把只包含质因子2、3和5的数称作丑数（Ugly Number）。例如6、8都是丑数，但14不是，因为它包含质因子7。习惯上我们把1当做是第一个丑数。求按从小到大的顺序的第N个丑数。

 1 # -*- coding:utf-8 -*-
 2 class Solution:
 3     def GetUglyNumber_Solution(self, index):
 4         if index <= 6:
 5             return index
 6         i2,i3,i5= 0,0,0
 7         dp = [0] * index
 8         dp[0] = 1
 9         for i in range(1,index):
10             next2 = dp[i2] * 2
11             next3 = dp[i3] * 3
12             next5 = dp[i5] * 5
13             dp[i] = min(next2,min(next3,next5))
14             if dp[i] == next2:
15                 i2 += 1
16             if dp[i] == next3:
17                 i3 += 1
18             if dp[i] == next5:
19                 i5 += 1
20         return dp[index-1]
21         # write code here

posted on 2019-06-14 13:57 Sempron2800+ 阅读(144) 评论(0) 编辑收藏举报