How to validate two binary trees have same content (integers) but may have different sturcture?

Question

This was asked today at Amazon interview -

Given two Binary Trees (not BST). Each node of both trees has an integer value. Validate whether both trees have the same integers, there could be repetitive integers.

Example
Tree1:
5
1 6
5 4 3 6

Tree2:
1
3 4
6 5

Output
Identical integers

Sample C/C++/Java code would be helpful.