Update 0056.合并区间，添加C#

problems/0056.合并区间.md

@@ -336,6 +336,32 @@ impl Solution {
     }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public int[][] Merge(int[][] intervals)
+    {
+        if (intervals.Length == 0)
+            return intervals;
+        Array.Sort(intervals, (a, b) => a[0] - b[0]);
+        List<List<int>> res = new List<List<int>>();
+        res.Add(intervals[0].ToList());
+        for (int i = 1; i < intervals.Length; i++)
+        {
+            if (res[res.Count - 1][1] >= intervals[i][0])
+            {
+                res[res.Count - 1][1] = Math.Max(res[res.Count - 1][1], intervals[i][1]);
+            }
+            else
+            {
+                res.Add(intervals[i].ToList());
+            }
+        }
+        return res.Select(x => x.ToArray()).ToArray();
+    }
+}
+```
 
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