Day384

README.md

@@ -379,5 +379,6 @@ problems from
 * [Day 381](https://github.com/vaskoz/dailycodingproblem-go/issues/768)
 * [Day 382](https://github.com/vaskoz/dailycodingproblem-go/issues/770)
 * [Day 383](https://github.com/vaskoz/dailycodingproblem-go/issues/772)
+* [Day 384](https://github.com/vaskoz/dailycodingproblem-go/issues/776)
 * [Day 385](https://github.com/vaskoz/dailycodingproblem-go/issues/774)
 

day384/problem.go

@@ -0,0 +1,44 @@
+package day384
+
+import (
+	"errors"
+	"sort"
+)
+
+// nolint
+var errImpossibleTarget = errors.New("impossible to make target change with denominations")
+
+const MaxInt = int(^uint(0) >> 1)
+
+// FewestCoinsBrute returns the fewest required coins to make target
+// in change.
+// Returns an error if it's not possible.
+func FewestCoinsBrute(denom []int, target int) (int, error) {
+	copied := append([]int{}, denom...)
+	sort.Sort(sort.Reverse(sort.IntSlice(copied)))
+
+	return fewestCoinsBrute(copied, target, MaxInt)
+}
+
+func fewestCoinsBrute(denom []int, target, coinsSoFar int) (int, error) {
+	if target < 0 || coinsSoFar < 0 {
+		return 0, errImpossibleTarget
+	} else if target == 0 {
+		return 0, nil
+	}
+
+	smallest := MaxInt
+
+	for _, d := range denom {
+		if res, err := fewestCoinsBrute(denom, target-d, coinsSoFar-1); err == nil && res < smallest {
+			smallest = res
+			coinsSoFar = res
+		}
+	}
+
+	if smallest == MaxInt {
+		return 0, errImpossibleTarget
+	}
+
+	return 1 + smallest, nil
+}

day384/problem_test.go

@@ -0,0 +1,33 @@
+package day384
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	denom         []int
+	target        int
+	expectedCoins int
+	expectedErr   error
+}{
+	{[]int{1, 5, 10}, 56, 7, nil},
+	{[]int{5, 8}, 15, 3, nil},
+	{[]int{5, 10}, 2, 0, errImpossibleTarget},
+}
+
+func TestFewestCoinsBrute(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if res, err := FewestCoinsBrute(tc.denom, tc.target); res != tc.expectedCoins || err != tc.expectedErr {
+			t.Errorf("Expected (%v,%v), got (%v,%v)", tc.expectedCoins, tc.expectedErr, res, err)
+		}
+	}
+}
+
+func BenchmarkFewestCoinsBrute(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			FewestCoinsBrute(tc.denom, tc.target) // nolint
+		}
+	}
+}