forked from lizeyang18/byteDanceAlgorithm
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathtest15.java
More file actions
47 lines (43 loc) · 1.3 KB
/
test15.java
File metadata and controls
47 lines (43 loc) · 1.3 KB
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
package byteDance;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
/**
* Created by lizeyang on 2020/5/13.
* 二叉树的先序非递归遍历 so easy~
*/
public class test15 {
//辅助栈实现，时间复杂度O(n)，空间复杂度O(n)
public static List<Integer> test(TreeNode root) {
List<Integer> list = new ArrayList<>();
if (root == null) {
return list;
}
Stack<TreeNode> stack = new Stack<>();
stack.push(root);
while (!stack.isEmpty()) {
TreeNode node = stack.pop();
list.add(node.val);
if (node.right != null) {
stack.push(node.right);
}
if (node.left != null) {
stack.push(node.left);
}
}
return list;
}
public static void main(String[] args) {
TreeNode root = new TreeNode(5);
root.left = new TreeNode(4);
root.right = new TreeNode(8);
root.left.left = new TreeNode(3);
root.right.left = new TreeNode(7);
root.right.left.left = new TreeNode(6);
root.right.right = new TreeNode(9);
List<Integer> res = test(root);
for (int i = 0; i < res.size(); i++) {
System.out.print(res.get(i) + " ");
}
}
}