Add Single Number II, Count Complete Tree Nodes

Author: hellomrsun

June-LeetCoding-Challenge/22-Single-Number-II/Single-Number-II.cs

@@ -0,0 +1,22 @@
+// Runtime: 96 ms, faster than 82.24% of C# online submissions for Single Number II.
+// Memory Usage: 25.3 MB, less than 40.54% of C# online submissions for Single Number II.
+public class Solution {
+    public int SingleNumber(int[] nums) {
+        var dict = new Dictionary<int, int>();
+        for(var i=0; i<nums.Length; i++){
+            if(!dict.ContainsKey(nums[i])){
+                dict[nums[i]] = 1;
+            }else {
+                dict[nums[i]] += 1;
+            }
+        }
+        
+        foreach(KeyValuePair<int,int> kv in dict){
+            if(kv.Value == 1){
+                return kv.Key;
+            }
+        }
+        
+        return -1;
+    }
+}

June-LeetCoding-Challenge/23-Count-Complete-Tree-Nodes/Count-Complete-Tree-Nodes.cs

@@ -0,0 +1,59 @@
+public class Solution
+{
+    //Solution 1
+    // Runtime: 100 ms, faster than 96.07% of C# online submissions for Count Complete Tree Nodes.
+    // Memory Usage: 32.3 MB, less than 97.70% of C# online submissions for Count Complete Tree Nodes.
+    public int CountNodes(TreeNode root)
+    {
+        var count = 0;
+        if (root == null)
+        {
+            return count;
+        }
+        DfsPreorderTraversal(root, ref count);
+        return count;
+    }
+    public void DfsPreorderTraversal(TreeNode node, ref int count)
+    {
+        if (node != null)
+        {
+            count++;
+        }
+        if (node.left != null)
+        {
+            DfsPreorderTraversal(node.left, ref count);
+        }
+        if (node.right != null)
+        {
+            DfsPreorderTraversal(node.right, ref count);
+        }
+        return;
+    }
+
+    //Solution 2
+    // Runtime: 112 ms, faster than 50.00% of C# online submissions for Count Complete Tree Nodes.
+    // Memory Usage: 32.5 MB, less than 87.10% of C# online submissions for Count Complete Tree Nodes.
+    public int CountNodes(TreeNode root)
+    {
+        if (root == null)
+        {
+            return 0;
+        }
+        return 1 + CountNodes(root.left) + CountNodes(root.right);
+    }
+}
+
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */