import java.util.*;
/* public class TreeNode { int val = 0; TreeNode left = null; TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
} */ public class Solution { boolean isSymmetrical(TreeNode pRoot) { if (pRoot == null){ return true; } if ((pRoot.left == null) != (pRoot.right == null)){ return false; } if (pRoot.left == null){ return true; } List toBeTraversed = new ArrayList<>(); toBeTraversed.add(pRoot.left); toBeTraversed.add(pRoot.right);
while(toBeTraversed.size() > 0){
TreeNode candidateOne = toBeTraversed.get(0);
TreeNode candidateTwo = toBeTraversed.get(1);
if (candidateOne.val != candidateTwo.val){
return false;
}
toBeTraversed.remove(0);
toBeTraversed.remove(0);
if ((candidateOne.left == null) == (candidateTwo.right == null)){
if (candidateOne.left != null){
toBeTraversed.add(candidateOne.left);
toBeTraversed.add(candidateTwo.right);
}
}else{
return false;
}
if ((candidateOne.right == null) == (candidateTwo.left == null)){
if (candidateOne.right != null){
toBeTraversed.add(candidateOne.right);
toBeTraversed.add(candidateTwo.left);
}
}else{
return false;
}
}
return true;
}
}