[leetcode]322. Coin Change找零钱

You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1.

Example 1:

Input: coins = [1, 2, 5], amount = 11
Output: 3 
Explanation: 11 = 5 + 5 + 1

Example 2:

Input: coins = [2], amount = 3
Output: -1

题意：

coins数组中，有1角、2角、5角面额的硬币，若需要凑出给定的amount面值，最少拿出几个硬币

思路：