Created
March 1, 2020 02:48
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101. Symmetric Tree
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/** | |
* Definition for a binary tree node. | |
* public class TreeNode { | |
* int val; | |
* TreeNode left; | |
* TreeNode right; | |
* TreeNode(int x) { val = x; } | |
* } | |
*/ | |
class Solution { | |
static int rootValue; | |
public boolean isSymmetric(TreeNode root) { | |
if (root == null) { | |
return true; | |
} | |
rootValue = root.val; | |
List<Integer> leftTravasalResult = new ArrayList<>(); | |
travasalLeftTree(leftTravasalResult, root); | |
List<Integer> rightTravasalResult = new ArrayList<>(); | |
travasalRightTree(rightTravasalResult, root); | |
if (leftTravasalResult.size() != rightTravasalResult.size()) { | |
return false; | |
} | |
for (int i = 0; i < leftTravasalResult.size(); i++) { | |
if (leftTravasalResult.get(i) != rightTravasalResult.get(i)) { | |
return false; | |
} | |
} | |
return true; | |
} | |
private static void travasalLeftTree(List<Integer> leftTravasalResult, TreeNode node) { | |
if (node == null) { | |
leftTravasalResult.add(null); | |
return; | |
} | |
leftTravasalResult.add(node.val); | |
travasalLeftTree(leftTravasalResult, node.left); | |
if (node.val == rootValue) { | |
return; | |
} | |
travasalLeftTree(leftTravasalResult, node.right); | |
} | |
private static void travasalRightTree(List<Integer> rightTravasalResult, TreeNode node) { | |
if (node == null) { | |
rightTravasalResult.add(null); | |
return; | |
} | |
rightTravasalResult.add(node.val); | |
travasalRightTree(rightTravasalResult, node.right); | |
if (node.val == rootValue) { | |
return; | |
} | |
travasalRightTree(rightTravasalResult, node.left); | |
} | |
} |
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