#322

Coin Change

MediumDynamic Programming

You are given an integer array coins of coin denominations and an integer amount. Return the fewest number of coins needed to make up amount. If it cannot be made, return -1. You have an infinite supply of each coin.

Example

coins = [1, 2, 5], amount = 11  => 3   // 5 + 5 + 1
coins = [2], amount = 3         => -1

Implement

function CoinChange(coins: int[], amount: int) -> int

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BAML docs

baml describe

Search the BAML stdlib (260 symbols). Try a type, function, or method name.

Basics

let x = 0;

mutable binding

let nums: int[] = [];

typed binding

function Add(a: int, b: int) -> int {
  return a + b;
}

Control flow

if (x > 0) {
  ...
} else {
  ...
}

while (i < n) {
  i += 1;
}

for (x in nums) {
  ...
}

iterate values

break;   continue;   return v;

Arrays

nums.length()

nums[i]

read (0-indexed)

nums[i] = v

write

nums.push(x)

nums.pop()

returns T? (optional)

nums.slice(a, b)   nums.reverse()

nums.sort_by_key(k)   nums.sort_by(cmp)

returns a sorted copy (no bare .sort())

Maps (use string keys)

let m: map<string, int> = {};

m.set("a", 1);

m.get("a")

returns int? (null if absent)

m.has("a")   m.keys()

m.set(n.to_string(), true);

int keys are unsupported: convert to string

Strings

s.length()

number of characters

s.char_at(i)   s.substring(a, b)

s.split(",")   s.to_lower_case()

c.is_alphanumeric()   c == "a"

Numbers

a / b

integer division

a % b

remainder

x.abs()   x.pow(e)   x.min(y)   x.max(y)

x & 1   x >> 1   x << 2   x ^ y

bitwise ops

n.to_string()

value to string

int.parse(s)

string to int

Optionals & null

let node: ListNode? = null;

if (x == null) {
  return 0;
}
// x is non-null below

guard-and-return narrows the type

Classes

class ListNode {
  val int
  next ListNode?
}

ListNode { val: 1, next: null }

construct with { }

node.val   node.next