Rrecursion1
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10class Solution {
private boolean isMirror(TreeNode t1,TreeNode t2){
if(t1==null && t2==null) return true;
if(t1==null || t2==null) return false;
return t1.val==t2.val&&isMirror(t1.left,t2.right)&&isMirror(t1.right,t2.left);
}
public boolean isSymmetric(TreeNode root) {
return isMirror(root,root);
}
}
Iteration: BFS1
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19class Solution {
public boolean isSymmetric(TreeNode root) {
LinkedList<TreeNode> queue=new LinkedList<>();
queue.push(root);
queue.push(root);
while(!queue.isEmpty()){
TreeNode t1=queue.poll();
TreeNode t2=queue.poll();
if(t1==null && t2==null) continue;
if(t1==null || t2==null) return false;
if(t1.val!=t2.val) return false;
queue.push(t1.left);
queue.push(t2.right);
queue.push(t1.right);
queue.push(t2.left);
}
return true;
}
}