Merge pull request #2389 from eeee0717/master

Update.买卖股票的最佳时机2，添加C#

problems/1005.K次取反后最大化的数组和.md

@@ -322,6 +322,29 @@ object Solution {
 }
 ```
 
+### C#
+```csharp
+public class Solution
+{
+    public int LargestSumAfterKNegations(int[] nums, int k)
+    {
+        int res = 0;
+        Array.Sort(nums, (a, b) => Math.Abs(b) - Math.Abs(a));
+        for (int i = 0; i < nums.Length; i++)
+        {
+            if (nums[i] < 0 && k > 0)
+            {
+                nums[i] *= -1;
+                k--;
+            }
+        }
+        if (k % 2 == 1) nums[nums.Length - 1] *= -1;
+        foreach (var item in nums) res += item;
+        return res;
+    }
+}
+```
+
 
 
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