leetcode uglynumber

最新推荐文章于 2025-09-08 16:25:29 发布

怒吃树

最新推荐文章于 2025-09-08 16:25:29 发布

阅读量254

点赞数

CC 4.0 BY-SA版权

文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/menghan1224/article/details/51659988

本文介绍了一种高效算法来找到第n个丑数。丑数是指只包含2、3、5这三个质因数的正整数。文章提供了一个具体的Java实现方案，通过维护三个动态索引来跟踪最小丑数。

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

如何寻找第n个丑数？

维护2、3、5三个链表作为索引，每次寻找min(result[index2]*2,result[index3]*3,result[index5]*5)

public int nthUglyNumber(int n) {
    int[] result=new int[n];
    result[0]=1;
    int index2=0,index3=0,index5=0;
    int count=1;
    for(int i=1;i<n;i++)
    {
      result[i]=min(result[index2]*2,result[index3]*3,result[index5]*5);
        if(result[i]==result[index2]*2)
            index2++;
        if(result[i]==result[index3]*3)
            index3++;
        if(result[i]==result[index5]*5)
            index5++;
    }

    return result[n-1];
}
public int min(int a,int b,int c)
{
    int min=a<b?a:b;
    return min<c?min:c;
}