-
Notifications
You must be signed in to change notification settings - Fork 2
/
InorderTraversalBinaryTree.java
99 lines (86 loc) · 2.16 KB
/
InorderTraversalBinaryTree.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
package Leetcode;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
/**
* @author kalpak
*
* Given the root of a binary tree, return the inorder traversal of its nodes' values.
*
* Example 1:
* Input: root = [1,null,2,3]
* Output: [1,3,2]
*
*
* Example 2:
* Input: root = []
* Output: []
*
*
* Example 3:
* Input: root = [1]
* Output: [1]
*
*
* Example 4:
* Input: root = [1,2]
* Output: [2,1]
*
*
* Example 5:
* Input: root = [1,null,2]
* Output: [1,2]
*
*
* Constraints:
*
* The number of nodes in the tree is in the range [0, 100].
* -100 <= Node.val <= 100
*
*
* Follow up:
*
* Recursive solution is trivial, could you do it iteratively?
*/
public class InorderTraversalBinaryTree {
public static List<Integer> inorderTraversal(TreeNode root) {
List<Integer> result = new ArrayList<>();
doInorderTraversal(root, result);
return result;
}
private static void doInorderTraversal(TreeNode root, List<Integer> result) {
// Base case
if(root == null)
return;
// Inorder traversal : Left -> Root -> Right
doInorderTraversal(root.left, result);
result.add(root.val);
doInorderTraversal(root.right, result);
return;
}
public static List<Integer> inorderTraversalIterative(TreeNode root) {
List<Integer> result = new ArrayList<>();
Deque<TreeNode> stack = new ArrayDeque<>();
if(root == null)
return result;
TreeNode current = root;
while(current != null || !stack.isEmpty()) {
while(current != null) {
stack.push(current);
current = current.left;
}
current = stack.pop();
result.add(current.val);
current = current.right;
}
return result;
}
public static void main(String[] args) {
TreeNode root = new TreeNode(1);
root.right = new TreeNode(2);
root.right.left = new TreeNode(3);
System.out.println(inorderTraversal(root));
System.out.println(inorderTraversalIterative(root));
}
}