Coin Change II

Coin Change II is a Medium Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Dynamic Programming (DP) Patterns pattern, in the 1D Array (Coin Change / Unbounded Knapsack Style) subpattern.

Problem statement

You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money.

Return the number of combinations that make up that amount. If that amount of money cannot be made up by any combination of the coins, return 0.

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

The answer is guaranteed to fit into a signed 32-bit integer.

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 = [2] Output: 0 Explanation: the amount of 3 cannot be made up just with coins of 2.

Example 3:

Input: amount = 10, coins = [10] Output: 1

Constraints:

- 1 <= coins.length <= 300

- 1 <= coins[i] <= 5000

- All the values of coins are unique.

- 0 <= amount <= 5000

Topics and companies

Topics: Array, Dynamic Programming.

Reported in interviews at Bloomberg, Facebook, Google, Microsoft, Yahoo.

How to practise Coin Change II on Thita.ai

Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n * m) time and O(m) space.

Open Coin Change II in the code editor, or read the Coin Change II editorial for a worked solution with its approach and complexity analysis.

Where Coin Change II sits in the DSA pattern sheet

Problems related to Coin Change II

Other problems that use the same 1D Array (Coin Change / Unbounded Knapsack Style) and Dynamic Programming (DP) Patterns techniques:

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