Same Tree

Problem: Same Tree

This is a typical depth-first search problem so no need to explain more. You can also use stacks to solve this problem instead of complex and time-consuming recursion.

Code in Python:

class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        if not p and not q: return True
        elif p and q:
            if p.val == q.val:
                if p.left and q.left:
                    if self.isSameTree(p.left, q.left):
                        if p.right and q.right:
                            return self.isSameTree(p.right, q.right)
                        elif not p.right and not q.right:
                            return True
                elif not p.left and not q.left:
                    if p.right and q.right:
                        return self.isSameTree(p.right, q.right)
                    elif not p.right and not q.right:
                        return True
        return False