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Write a program to find the n
-th ugly number.
Ugly numbers are positive numbers whose prime factors only include 2, 3, 5
. For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12
is the sequence of the first 10
ugly numbers.
Note that 1
is typically treated as an ugly number.
Hint:
isUgly
for every number until you reach the nth one. Most numbers are not ugly. Try to focus your effort on generating only the ugly ones.Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
代码如下:
public class Solution { public int nthUglyNumber(int n) { int [] ugly=new int[n]; ugly[0]=1; int index2=0; int index3=0; int index5=0; int factor2=2; int factor3=3; int factor5=5; for(int i=1;i<n;i++){ int min=Math.min(Math.min(factor2,factor3),factor5); ugly[i]=min; if(factor2==min){ factor2=2*ugly[++index2]; } if(factor3==min){ factor3=3*ugly[++index3]; } if(factor5==min){ factor5=5*ugly[++index5]; } } return ugly[n-1]; } }
运行结果:
(medium)LeetCode 264.Ugly Number II
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原文地址:http://www.cnblogs.com/mlz-2019/p/4742924.html