feat: add coin change problem

dp/coin_change_problem.go

@@ -0,0 +1,15 @@
+package dp
+
+func getWays(n int64, coins []int64) int64 {
+	ways := make([]int64, n+1)
+	ways[0] = 1
+
+	for _, coin := range coins {
+		var i int64
+		for i = coin; i <= n; i++ {
+			ways[i] += ways[i-coin]
+		}
+	}
+
+	return ways[n]
+}

dp/coin_change_problem_test.go

@@ -0,0 +1,37 @@
+package dp
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type CoinChangeTestCase struct {
+	n      int64
+	c      []int64
+	result int64
+}
+
+func TestCoinChangeProblem(t *testing.T) {
+	tests := []CoinChangeTestCase{
+		{
+			n:      3,
+			c:      []int64{8, 3, 1, 2},
+			result: 3,
+		},
+		{
+			n:      4,
+			c:      []int64{1, 2, 3},
+			result: 4,
+		},
+		{
+			n:      10,
+			c:      []int64{2, 5, 3, 6},
+			result: 5,
+		},
+	}
+
+	for _, test := range tests {
+		assert.Equal(t, test.result, getWays(test.n, test.c))
+	}
+}