【剑指offer】丑数（python）

我们只用比较3个数：用于乘2的最小的数、用于乘3的最小的数，用于乘5的最小的。

# -*- coding:utf-8 -*-
class Solution:
    def GetUglyNumber_Solution(self, index):
        # write code here
        if index <= 6:
            return index
        i2 = 0
        i3 = 0
        i5 = 0
        dp = [0 for i in range(index)]
        dp[0] = 1
        for i in range(1, index):
            next2 = dp[i2]*2
            next3 = dp[i3]*3
            next5 = dp[i5]*5
            dp[i] = min(next2,min(next3,next5))
            if dp[i] == next2:
                i2+=1
            if dp[i] == next3:
                i3+=1
            if dp[i] == next5:
                i5+=1
        return dp[index-1]