心得

簡單來說就是輸入數字x，找出x的因數並找出相乘會等於x的兩個數字且兩數字相減最接近0的組合，大的放前面小的放後面以int[]的型態回傳。

問題

For a web developer, it is very important to know how to design a web page’s size. So, given a specific rectangular web page’s area, your job by now is to design a rectangular web page, whose length L and width W satisfy the following requirements:

1. The area of the rectangular web page you designed must equal to the given target area.

2. The width W should not be larger than the length L, which means L >= W.

3. The difference between length L and width W should be as small as possible.

You need to output the length L and the width W of the web page you designed in sequence.

Example:

Input: 4
Output: [2, 2]
Explanation: The target area is 4, and all the possible ways to construct it are [1,4], [2,2], [4,1]. 
But according to requirement 2, [1,4] is illegal; according to requirement 3,  [4,1] is not optimal compared to [2,2]. So the length L is 2, and the width W is 2.

Note:

1. The given area won’t exceed 10,000,000 and is a positive integer
2. The web page’s width and length you designed must be positive integers.

答案

1. 我的笨方法

   public class Solution {
       public int[] ConstructRectangle(int area) {
           int num1 = Enumerable
               .Range(1, (int)Math.Sqrt(area))
               .Where(x => area % x == 0)
               .OrderBy(x => Math.Abs((area / x) - x))
               .FirstOrDefault();
           int num2 = area / num1;
           return num1 > num2 ? new int[] { num1, num2 } : new int[] { num2, num1 };
       }
   }

2. Top Solution的神方法

   public class Solution {
       public int[] ConstructRectangle(int area) {
           int w = (int)Math.Sqrt(area);
           while( area % w != 0){
               w--;
           }
           return new int[] { area / w, w };
       }
   }