Add problem 322 - Coin Change

Author: anirudhology

problems/dynamic_programming/coin_change.go

@@ -0,0 +1,27 @@
+package dynamic_programming
+
+import "math"
+
+func CoinChange(coins []int, amount int) int {
+	// Special case
+	if len(coins) == 0 || amount < 0 {
+		return -1
+	}
+	// Lookup table to store number of ways to make amount i
+	lookup := make([]int, amount+1)
+	for i := 1; i <= amount; i++ {
+		lookup[i] = math.MaxInt64
+		for _, coin := range coins {
+			if coin <= i {
+				difference := lookup[i-coin]
+				if difference != math.MaxInt64 {
+					lookup[i] = min(lookup[i], 1+difference)
+				}
+			}
+		}
+	}
+	if lookup[amount] == math.MaxInt64 {
+		return -1
+	}
+	return lookup[amount]
+}

tests/dynamic_programming/coin_change_test.go

@@ -0,0 +1,49 @@
+package dynamic_programming_test
+
+import (
+	"testing"
+
+	"github.com/anirudhology/leetcode-go/problems/dynamic_programming"
+)
+
+func TestCoinChange(t *testing.T) {
+	// Test case for null coins array
+	if result := dynamic_programming.CoinChange(nil, 5); result != -1 {
+		t.Errorf("Expected -1, got %d", result)
+	}
+
+	// Test case for empty coins array
+	if result := dynamic_programming.CoinChange([]int{}, 5); result != -1 {
+		t.Errorf("Expected -1, got %d", result)
+	}
+
+	// Test case for negative amount
+	if result := dynamic_programming.CoinChange([]int{1, 2, 5}, -5); result != -1 {
+		t.Errorf("Expected -1, got %d", result)
+	}
+
+	// Test case for amount 0
+	if result := dynamic_programming.CoinChange([]int{1, 2, 5}, 0); result != 0 {
+		t.Errorf("Expected 0, got %d", result)
+	}
+
+	// Test case for amount that can't be reached
+	if result := dynamic_programming.CoinChange([]int{2}, 3); result != -1 {
+		t.Errorf("Expected -1, got %d", result)
+	}
+
+	// Test case for amount with exact coin matches
+	if result := dynamic_programming.CoinChange([]int{1, 2, 5}, 5); result != 1 {
+		t.Errorf("Expected 1, got %d", result)
+	}
+
+	// Test case for amount with no exact match but can be reached
+	if result := dynamic_programming.CoinChange([]int{1, 2, 5}, 11); result != 3 {
+		t.Errorf("Expected 3, got %d", result)
+	}
+
+	// Test case for large amount
+	if result := dynamic_programming.CoinChange([]int{1, 2, 5}, 100); result != 20 {
+		t.Errorf("Expected 20, got %d", result)
+	}
+}