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103:二叉树的锯齿形层序遍历

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huangge1199 2021-04-09 11:26:18 +08:00
parent 33abfefdf9
commit f6ebc8cef4
1 changed files with 31 additions and 37 deletions
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68
LeetCode/src/main/java/leetcode/editor/cn/BinaryTreeZigzagLevelOrderTraversal.java
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@ -27,10 +27,7 @@ package leetcode.editor.cn;
import com.code.leet.entiy.TreeNode; import com.code.leet.entiy.TreeNode;
import java.util.ArrayList; import java.util.*;
import java.util.Arrays;
import java.util.List;
import java.util.Stack;
//103:二叉树的锯齿形层序遍历 //103:二叉树的锯齿形层序遍历
public class BinaryTreeZigzagLevelOrderTraversal { public class BinaryTreeZigzagLevelOrderTraversal {
@ -59,40 +56,37 @@ public class BinaryTreeZigzagLevelOrderTraversal {
* } * }
*/ */
class Solution { class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) { public List<List<Integer>> zigzagLevelOrder(TreeNode root) {List<List<Integer>> ans = new LinkedList<List<Integer>>();
List<List<Integer>> result = new ArrayList<>(); if (root == null) {
Stack<TreeNode> stack1 = new Stack<>(); return ans;
Stack<TreeNode> stack2 = new Stack<>();
stack1.push(root);
TreeNode temp;
List<Integer> list;
while (!stack1.isEmpty() || !stack2.isEmpty()) {
list = new ArrayList<>();
while (!stack1.isEmpty()) {
temp = stack1.pop();
list.add(temp.val);
if (temp.left != null) {
stack2.push(temp.left);
}
if (temp.right != null) {
stack2.push(temp.right);
}
result.add(list);
}
list = new ArrayList<>();
while (!stack2.isEmpty()) {
temp = stack2.pop();
list.add(temp.val);
if (temp.right != null) {
stack1.push(temp.right);
}
if (temp.left != null) {
stack1.push(temp.left);
}
result.add(list);
}
} }
return result;
Queue<TreeNode> nodeQueue = new LinkedList<TreeNode>();
nodeQueue.offer(root);
boolean isOrderLeft = true;
while (!nodeQueue.isEmpty()) {
Deque<Integer> levelList = new LinkedList<Integer>();
int size = nodeQueue.size();
for (int i = 0; i < size; ++i) {
TreeNode curNode = nodeQueue.poll();
if (isOrderLeft) {
levelList.offerLast(curNode.val);
} else {
levelList.offerFirst(curNode.val);
}
if (curNode.left != null) {
nodeQueue.offer(curNode.left);
}
if (curNode.right != null) {
nodeQueue.offer(curNode.right);
}
}
ans.add(new LinkedList<Integer>(levelList));
isOrderLeft = !isOrderLeft;
}
return ans;
} }
} }
//leetcode submit region end(Prohibit modification and deletion) //leetcode submit region end(Prohibit modification and deletion)