leetcode

Author: ayoubzulfiqar

BinaryTreePostorderTraversal/binary_tree_postorder_traversal.go

@@ -1,40 +1,47 @@
 package main
 
+// Definition for a binary tree node.
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
 func postorderTraversal(root *TreeNode) []int {
 
-    // empty tree
-    if root == nil {
-        return []int{}
-    }
-
-    nodeStack := []*TreeNode{root}  // the nodes
-    nodesSeen := []bool{false} // whether a node already seen
-    values := make([]int, 0)  // values in postorder
-
-    // traverse tree with stack
-    for len(nodeStack) != 0 {
-        node := nodeStack[len(nodeStack)-1]
-
-        // leaf -> node seen; or children traversed
-        if (node.Left == nil && node.Right == nil) || nodesSeen[len(nodesSeen)-1] {
-            values = append(values, node.Val)
-            nodeStack = nodeStack[:len(nodeStack)-1]  // pop node
-            nodesSeen = nodesSeen[:len(nodesSeen)-1]
-            continue
-        }
-
-        nodesSeen[len(nodesSeen)-1] = true  // mark node as seen
-
-        // push children on stack
-        if node.Right != nil {
-            nodeStack = append(nodeStack, node.Right)
-            nodesSeen = append(nodesSeen, false)
-        }
-        if node.Left != nil {  // traversed first, therefore put on stack second
-            nodeStack = append(nodeStack, node.Left)
-            nodesSeen = append(nodesSeen, false)
-        }
-    }
-
-    return values
-}
+	// empty tree
+	if root == nil {
+		return []int{}
+	}
+
+	nodeStack := []*TreeNode{root} // the nodes
+	nodesSeen := []bool{false}     // whether a node already seen
+	values := make([]int, 0)       // values in postorder
+
+	// traverse tree with stack
+	for len(nodeStack) != 0 {
+		node := nodeStack[len(nodeStack)-1]
+
+		// leaf -> node seen; or children traversed
+		if (node.Left == nil && node.Right == nil) || nodesSeen[len(nodesSeen)-1] {
+			values = append(values, node.Val)
+			nodeStack = nodeStack[:len(nodeStack)-1] // pop node
+			nodesSeen = nodesSeen[:len(nodesSeen)-1]
+			continue
+		}
+
+		nodesSeen[len(nodesSeen)-1] = true // mark node as seen
+
+		// push children on stack
+		if node.Right != nil {
+			nodeStack = append(nodeStack, node.Right)
+			nodesSeen = append(nodesSeen, false)
+		}
+		if node.Left != nil { // traversed first, therefore put on stack second
+			nodeStack = append(nodeStack, node.Left)
+			nodesSeen = append(nodesSeen, false)
+		}
+	}
+
+	return values
+}