binary_tree_preorder_traversal

hitzzc · hitzzc · commit 2e2369a50a81 · 2016-10-12T22:48:56.000+08:00
diff --git a/README.md b/README.md
@@ -127,6 +127,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [141. Linked List Cycle](https://github.com/hitzzc/go-leetcode/tree/master/linked_list_cycle)
 #### [142. Linked List Cycle II](https://github.com/hitzzc/go-leetcode/tree/master/linked_list_cycle_II)
 #### [143. reorder list](https://github.com/hitzzc/go-leetcode/tree/master/reorder_list)
+#### [144. binary tree preorder traversal](https://github.com/hitzzc/go-leetcode/tree/master/binary_tree_preorder_traversal)
 
 
 
diff --git a/binary_tree_preorder_traversal/binary_tree_preorder_traversal.go b/binary_tree_preorder_traversal/binary_tree_preorder_traversal.go
@@ -0,0 +1,29 @@
+package binary_tree_preorder_traversal
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func preorderTraversal(root *TreeNode) []int {
+	rets := []int{}
+	if root == nil {
+		return rets
+	}
+	stack := []*TreeNode{}
+	p := root
+	for len(stack) != 0 || p != nil {
+		for p != nil {
+			rets = append(rets, p.Val)
+			stack = append(stack, p)
+			p = p.Left
+		}
+		if len(stack) != 0 {
+			p = stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+			p = p.Right
+		}
+	}
+	return rets
+}
