Coin Change II

Problem

Given a target amount and an array of coin denominations, return the number of distinct combinations (order doesn't matter) that make up that amount, using any number of each coin.

Examples

Example 1

Input:amount = 5, coins = [1,2,5]

Output:4

Constraints

1 <= coins.length <= 300

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How to approach it: the 2-D Dynamic Programming pattern

The same DP idea as 1-D, but the state depends on two indices — often two positions in a grid, or a position in each of two sequences being compared.

Look for this pattern when

You're comparing two sequences (finding a longest common subsequence, edit distance).
You're computing paths or optimal values across a 2-D grid.

Read the full 2-D Dynamic Programming guide →

Video walkthroughs

Original problem on LeetCode ↗