add new solutions

solutions/4/q450/solution.go

@@ -0,0 +1,46 @@
+package q450
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func del(node *TreeNode) *TreeNode {
+	if node == nil || node.Left == nil && node.Right == nil {
+		return nil // is leaf
+	}
+	if node.Left == nil {
+		return node.Right
+	}
+	if node.Right == nil {
+		return node.Left
+	}
+
+	p := node.Left
+	for p.Right != nil {
+		p = p.Right
+	}
+	p.Right = node.Right
+	return node.Left
+}
+
+func findAndDel(node **TreeNode, key int) {
+	if *node == nil {
+		return
+	}
+	if (**node).Val == key {
+		*node = del(*node)
+	} else if key < (**node).Val {
+		findAndDel(&(**node).Left, key)
+	} else {
+		findAndDel(&(**node).Right, key)
+	}
+}
+
+func deleteNode(root *TreeNode, key int) *TreeNode {
+	findAndDel(&root, key)
+	return root
+}
+
+var _ = deleteNode