feat: add LeetCode problem 450

leetcode/src/450.c

@@ -0,0 +1,44 @@
+/*
+ * Deletes a node with the given key from a Binary Search Tree (BST).
+ * Handles three cases: deleting a leaf node, a node with one child,
+ * and a node with two children (replaced by its in-order successor).
+ */
+
+struct TreeNode* deleteNode(struct TreeNode* root, int key)
+{
+    if (root == NULL)
+        return NULL;
+
+    if (key < root->val)
+    {
+        root->left = deleteNode(root->left, key);
+    }
+    else if (key > root->val)
+    {
+        root->right = deleteNode(root->right, key);
+    }
+    else
+    {
+        if (root->left == NULL && root->right == NULL)
+        {
+            return NULL;
+        }
+        else if (root->left == NULL)
+        {
+            return root->right;
+        }
+        else if (root->right == NULL)
+        {
+            return root->left;
+        }
+        else
+        {
+            struct TreeNode* min_node = root->right;
+            while (min_node->left != NULL) min_node = min_node->left;
+
+            root->val = min_node->val;
+            root->right = deleteNode(root->right, min_node->val);
+        }
+    }
+    return root;
+}