Leetcode 322 Coin Change

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:
coins =

[1, 2, 5]

, amount =

11

return

3

(11 = 5 + 5 + 1)

Example 2:
coins =

[2]

, amount =

3

return

-1

.

Note:
You may assume that you have an infinite number of each kind of coin.

基本的找零问题加上额外判断。这里先把所有元素设为amount＋1，然后最后再判断。

class Solution(object):
def coinChange(self, coins, amount):
tot = [amount+1 for i in range(amount+1)]
tot[0] = 0
for i in range(1,amount+1):
for x in coins:
if x <= i:
tot[i] = min(tot[i-x]+1,tot[i])
if tot[-1] == amount+1:
return -1
return tot[-1]