leetcode 65: Same Tree

Same TreeSep
3 '12

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

bad one recursive.

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
// Start typing your Java solution below
// DO NOT write main() function
if(p==null && q==null) return true;
else if( p==null || q==null) return false;
if( p.val != q.val) return false;
else return isSameTree( p.left, q.left) && isSameTree(p.right, q.right);

}
}

good one iterative.

public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
// Start typing your Java solution below
// DO NOT write main() function
Queue<TreeNode> q1 = new LinkedList<TreeNode>();
Queue<TreeNode> q2 = new LinkedList<TreeNode>();

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

while( !q1.isEmpty() && !q2.isEmpty() ) {
TreeNode x = q1.poll();
TreeNode y = q2.poll();

if(x==null) {
if( y!=null) return false;
else continue;
}

if(y==null || x.val!=y.val) return false;

q1.offer( x.left);
q1.offer( x.right);
q2.offer(y.left);
q2.offer(y.right);
}

return true;
}
}