Checking whether two numbers are permutation of each other?

Question

Given two numbers a, b such that 1 <= a , b <= 10000000000 (10^10). My problem is to check whether the digits in them are permutation of each other or not. What is the fas

Answer 1

Is it homework?

Calculate number of appearances of each digit and compare them, if they are same then one number can be converted to other using permutation.