leetcode 264: Ugly Number II

最新推荐文章于 2022-05-01 20:36:55 发布

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最新推荐文章于 2022-05-01 20:36:55 发布

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本文介绍了一种求解第N个丑数的有效算法。丑数是指只包含质因数2、3和5的正整数。通过维护三个列表分别跟踪乘以2、3和5后的数，该算法能高效地找到指定位置的丑数。

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Ugly Number II

Total Accepted: 2920 Total Submissions: 15174

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.

[思路]

[CODE]

public class Solution {
    public int nthUglyNumber(int n) {
        int u = 0;
        List<Integer> l1 = new LinkedList<Integer>();
        List<Integer> l2 = new LinkedList<Integer>();
        List<Integer> l3 = new LinkedList<Integer>();
        l1.add(1);
        l2.add(1);
        l3.add(1);
        
        for(int i=0; i<n; i++) {
            u = Math.min( Math.min(l1.get(0), l2.get(0)), l3.get(0));
            
            if(l1.get(0) == u) l1.remove(0);
            if(l2.get(0) == u) l2.remove(0);
            if(l3.get(0) == u) l3.remove(0);
            
            l1.add(u*2);
            l2.add(u*3);
            l3.add(u*5);
        }
        return u;
    }
}