Leetcode 658: Find K Closest Elements

Posted 2020-10-21 Keep walking

Given a sorted array, two integers k and x, find the k closest elements to x in the array. The result should also be sorted in ascending order. If there is a tie, the smaller elements are always preferred.

Example 1:

Input: [1,2,3,4,5], k=4, x=3
Output: [1,2,3,4]

 

Example 2:

Input: [1,2,3,4,5], k=4, x=-1
Output: [1,2,3,4]

 

Note:

1. The value k is positive and will always be smaller than the length of the sorted array.
2. Length of the given array is positive and will not exceed 104
3. Absolute value of elements in the array and x will not exceed 104

 1 public class Solution {
 2     public IList<int> FindClosestElements(int[] arr, int k, int x) {
 3         var result = new List<int>();
 4         
 5         if (arr == null || arr.Length == 0 || k <= 0) return result;
 6         
 7         if (k >= arr.Length) return arr.ToList();
 8         
 9         var index = FindIndex(arr, x);
10         
11         int i = index - 1, j = index;
12         
13         while (k > 0)
14         {
15             if ((i >= 0 && i < arr.Length) && (j >= 0 && j < arr.Length))
16             {
17                 var d1 = Math.Abs(x - arr[i]);
18                 var d2 = Math.Abs(x - arr[j]);
19                 
20                 if (d1 <= d2)
21                 {
22                     result.Add(arr[i]);
23                     i--;
24                 }
25                 else
26                 {
27                     result.Add(arr[j]);
28                     j++;
29                 }
30             }
31             else if (i >= 0 && i < arr.Length)
32             {
33                 result.Add(arr[i]);
34                 i--;
35             }
36             else if (j >= 0 && j < arr.Length)
37             {
38                 result.Add(arr[j]);
39                 j++;
40             }
41                         
42             k--;
43         }
44         
45         result.Sort();
46         
47         return result;
48     }
49     
50     private int FindIndex(int[] arr, int x)
51     {
52         int low = 0, high = arr.Length;
53         
54         while (low < high)
55         {
56             int mid = low + (high - low) / 2;
57             
58             if (arr[mid] == x)
59             {
60                 return mid;
61             }
62             else if (arr[mid] < x)
63             {
64                 low = mid + 1;
65             }
66             else
67             {
68                 high = mid;
69             }
70         }
71         
72         return low;
73     }
74 }