You are given coins of different denominations and a total amount of money. Write a function to compute the number of combinations that make up that amount. You may assume that you have infinite number of each kind of coin.
Example 1 Input: amount = 5, coins = [1, 2, 5] Output: 4 Explanation: there are four ways to make up the amount: 5=5 5=2+2+1 5=2+1+1+1 5=1+1+1+1+1 Example 2 Input: amount = 3, coins =  Output: 0 Explanation: the amount of 3 cannot be made up just with coins of 2. Example 3 Input: amount = 10, coins =  Output: 1
You may assume that you have an infinite number of each kind of coin.