#0066

Coin Change Minimum Coins

MediumDSA30 min20 XP

Problem

Given coin denominations and an amount, return the minimum number of coins needed to make that amount. Return -1 if impossible.

Why This Matters

This is the standard unbounded knapsack pattern: reuse previous answers to build larger amounts.

Function Signature

def coin_change(coins, amount):

Examples

Example 1

Inputcoins = [1, 2, 5], amount = 11

Output3

11 can be made as 5 + 5 + 1.

Constraints

Coins can be reused.
Return 0 when amount is 0.
Return -1 when impossible.

CodePython

def coin_change(coins, amount):
    """
    Input example: coins = [1, 2, 5], amount = 11
    Return: 3
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return -1

def coin_change(coins, amount):
    """
    Input example: coins = [1, 2, 5], amount = 11
    Return: 3
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return -1

Visible browser tests run here when available.

Testcases2 visible / 3 hidden categories

Reusable coins

Input[1,2,5], 11

Expected3

Two 5s and one 1 use three coins.

Impossible amount

Input[2], 3

Expected-1

Odd amount cannot be made from coin 2.

Hidden Test Categories

amount zerosingle exact coingreedy would fail