java Programming Problem Print Binary Tree from Top to Bottom
- 2021-07-01 07:26:13
- OfStack
This article example for everyone to share java from top to bottom to print out 2-tree specific code, for your reference, the specific content is as follows
github: Sword refers to all the test questions of offer programming
import java.util.ArrayList;
import java.util.Stack;
/**
*
* Sword finger offer Programming problem ( JAVA Realization ) -No. 1 22 Question: Print from top to bottom 2 Fork tree
*
* Title description
* Print from top to bottom 2 Each node of the cross tree, the nodes in the same layer are printed from left to right.
*
*/
public class Test22 {
ArrayList<Integer> arrayList = new ArrayList<>();
// Each layer is stacked in turn
Stack<TreeNode> stack1 = new Stack<>();
// From stack1 Elements out of the stack are added in turn stack2 , unified 1 Pass stack2 Find their word nodes and press them in stack1
Stack<TreeNode> stack2 = new Stack<>();
public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
if (root == null) {
return arrayList;// Empty returns
}
stack1.push(root);
while (!stack1.isEmpty()) {
while (!stack1.isEmpty()) {
TreeNode tmp = stack1.pop();
arrayList.add(tmp.val);
stack2.push(tmp);
}
while (!stack2.isEmpty()) {
TreeNode tmp2 = stack2.pop();
// Print from left to right, so the right subtree goes to the stack first
if (tmp2.right != null) {
stack1.push(tmp2.right);
}
if (tmp2.left != null) {
stack1.push(tmp2.left);
}
}
}
return arrayList;
}
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}
}
// Other methods
/**
public class Solution {
public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
ArrayList<Integer> list = new ArrayList<Integer>();
if(root == null) return list;
Deque<TreeNode> deque = new LinkedList<TreeNode>();
deque.add(root);
while(!deque.isEmpty()){
TreeNode t = deque.pop();
list.add(t.val);
if(t.left != null) deque.add(t.left);
if(t.right != null) deque.add(t.right);
}
return list;
}
}
*/