binary tree preorder traversal without recurrsion

Author: vfedorovatlas

binary-tree-preorder-traversal/Readme.md

@@ -0,0 +1,2 @@
+# Problem: 144. Binary Tree Preorder Traversal
+

binary-tree-preorder-traversal/main.go

@@ -0,0 +1,50 @@
+package binarytreepreordertraversal
+
+// TreeNode data structure
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+// Stack data structure that implements LIFO
+type Stack []*TreeNode
+
+// Push adds an item onto the stack.
+func (s *Stack) Push(node *TreeNode) {
+	*s = append(*s, node)
+}
+
+// Pop removes the most-recently-pushed item from the stack.
+func (s *Stack) Pop() *TreeNode {
+	arr := *s
+	last := len(arr) - 1
+	top := arr[last]
+	if len(arr) > 0 {
+		arr = arr[0:last]
+	} else {
+		arr = []*TreeNode{}
+	}
+	*s = arr
+	return top
+}
+
+// Nice explanation: https://www.hackerearth.com/practice/notes/iterative-tree-traversals/
+func preorderTraversal(root *TreeNode) []int {
+	ret := []int{}
+	if root == nil {
+		return ret
+	}
+	stack := Stack{root}
+	for len(stack) > 0 {
+		node := stack.Pop()
+		ret = append(ret, node.Val)
+		if node.Right != nil {
+			stack.Push(node.Right)
+		}
+		if node.Left != nil {
+			stack.Push(node.Left)
+		}
+	}
+	return ret
+}

binary-tree-preorder-traversal/main_test.go

@@ -0,0 +1,50 @@
+package binarytreepreordertraversal
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestPreorderTraversal(t *testing.T) {
+	testCases := []struct {
+		Input  *TreeNode
+		Output []int
+	}{
+		{
+			Input: &TreeNode{
+				Val:  1,
+				Left: nil,
+				Right: &TreeNode{
+					Val: 2,
+					Right: &TreeNode{
+						Val: 3,
+					},
+				},
+			},
+			Output: []int{1, 2, 3},
+		},
+		{
+			Input:  nil,
+			Output: []int{},
+		},
+		{
+			Input: &TreeNode{
+				Val: 3,
+				Left: &TreeNode{
+					Val: 1,
+				},
+				Right: &TreeNode{
+					Val: 2,
+				},
+			},
+			Output: []int{3, 1, 2},
+		},
+	}
+
+	for _, test := range testCases {
+		out := preorderTraversal(test.Input)
+		if !reflect.DeepEqual(test.Output, out) {
+			t.Errorf("expected to get %#v, but got %#v", test.Output, out)
+		}
+	}
+}

coverage.txt

@@ -0,0 +1,62 @@
+
+mode: atomic
+github.com/vfedoroff/leetcode/permutations/main.go:5.34,13.12 8 2
+github.com/vfedoroff/leetcode/permutations/main.go:33.2,33.15 1 2
+github.com/vfedoroff/leetcode/permutations/main.go:13.12,14.15 1 16
+github.com/vfedoroff/leetcode/permutations/main.go:14.15,15.16 1 5
+github.com/vfedoroff/leetcode/permutations/main.go:23.4,27.9 5 5
+github.com/vfedoroff/leetcode/permutations/main.go:15.16,17.5 1 2
+github.com/vfedoroff/leetcode/permutations/main.go:17.5,19.5 1 3
+github.com/vfedoroff/leetcode/permutations/main.go:28.4,31.4 2 11
+mode: atomic
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:3.39,5.22 2 1
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:8.2,9.27 2 1
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:15.2,17.10 3 1
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:5.22,7.3 1 0
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:9.27,10.27 1 2
+github.com/vfedoroff/leetcode/remove-duplicates-from-sorted-array/main.go:10.27,13.4 2 1
+mode: atomic
+github.com/vfedoroff/leetcode/remove-element/main.go:3.45,5.12 2 3
+github.com/vfedoroff/leetcode/remove-element/main.go:8.2,9.25 2 3
+github.com/vfedoroff/leetcode/remove-element/main.go:15.2,15.10 1 3
+github.com/vfedoroff/leetcode/remove-element/main.go:5.12,7.3 1 0
+github.com/vfedoroff/leetcode/remove-element/main.go:9.25,10.21 1 8
+github.com/vfedoroff/leetcode/remove-element/main.go:10.21,13.4 2 2
+mode: atomic
+github.com/vfedoroff/leetcode/reverse-integer/main.go:14.25,17.14 3 7
+github.com/vfedoroff/leetcode/reverse-integer/main.go:20.2,20.13 1 7
+github.com/vfedoroff/leetcode/reverse-integer/main.go:25.2,25.23 1 7
+github.com/vfedoroff/leetcode/reverse-integer/main.go:28.2,28.14 1 6
+github.com/vfedoroff/leetcode/reverse-integer/main.go:31.2,31.10 1 4
+github.com/vfedoroff/leetcode/reverse-integer/main.go:17.14,19.3 1 2
+github.com/vfedoroff/leetcode/reverse-integer/main.go:20.13,24.3 3 22
+github.com/vfedoroff/leetcode/reverse-integer/main.go:25.23,27.3 1 1
+github.com/vfedoroff/leetcode/reverse-integer/main.go:28.14,30.3 1 2
+mode: atomic
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:10.29,14.12 4 18
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:17.2,17.36 1 16
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:27.2,29.6 3 14
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:47.2,48.19 2 12
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:51.2,51.19 1 11
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:54.2,54.21 1 10
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:14.12,16.3 1 2
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:17.36,18.20 1 9
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:21.3,23.12 3 9
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:18.20,20.4 1 8
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:23.12,25.4 1 2
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:29.6,32.12 3 75
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:35.3,37.22 3 70
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:43.3,43.13 1 68
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:32.12,33.9 1 5
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:37.22,38.18 1 2
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:41.4,41.17 1 1
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:38.18,40.5 1 1
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:43.13,44.9 1 7
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:48.19,50.3 1 1
+github.com/vfedoroff/leetcode/string-to-integer-atoi/main.go:51.19,53.3 1 1
+mode: atomic
+github.com/vfedoroff/leetcode/two-sum/main.go:3.43,5.25 2 1
+github.com/vfedoroff/leetcode/two-sum/main.go:13.2,13.22 1 0
+github.com/vfedoroff/leetcode/two-sum/main.go:5.25,8.9 3 2
+github.com/vfedoroff/leetcode/two-sum/main.go:11.3,11.11 1 1
+github.com/vfedoroff/leetcode/two-sum/main.go:8.9,10.4 1 1

string-to-integer-atoi/main.go

@@ -53,3 +53,4 @@ func myAtoi(str string) int {
 	}
 	return prefix * num
 }
+