Update MonotonicStack.cs

Author: jijog-jijog

patterns/c#/MonotonicStack.cs

@@ -5,6 +5,7 @@ public class MonotonicStack {
  public int[] NextGreaterElement(int[] nums) {
  int n = nums.Length;
  int[] result = new int[n];
+ 
  Array.Fill(result, -1); // Default to -1 if no greater element exists
  Stack<int> stack = new Stack<int>(); // Stack stores indices
 
@@ -32,4 +33,4 @@ public int[] DailyTemperatures(int[] temperatures) {
  }
  return result;
  }
-}
+}