Same Tree

Recursive

/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if (p == null && q == null) {
return true;
} else if (p == null) {
return false;
} else if (q == null ) {
return false;
} else {
if (p.val != q.val) {
return false;
}
return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
}
}
}Iterative
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if ((p == null) ^ (q == null)) {
return false;
} else if (p == null && q == null) {
return true;
}

Queue<TreeNode> q1 = new LinkedList<TreeNode>();
Queue<TreeNode> q2 = new LinkedList<TreeNode>();

q1.offer(p);
q2.offer(q);

while (!q1.isEmpty() && !q2.isEmpty()) {
TreeNode pNode = q1.poll();
TreeNode qNode = q2.poll();

if ((pNode == null) ^ (qNode == null)) {
return false;
} else if (pNode == null && qNode == null) {
continue;
} else {
if (pNode.val != qNode.val) {
return false;
}
q1.offer(pNode.left);
q1.offer(pNode.right);
q2.offer(qNode.left);
q2.offer(qNode.right);
}
}
if (!q1.isEmpty() || !q2.isEmpty()) {
return false;
}
return true;
}
}