Merge 7cd9a47 into 174b145

README.md

@@ -332,3 +332,4 @@ problems from
 * [Day 338](https://github.com/vaskoz/dailycodingproblem-go/issues/675)
 * [Day 339](https://github.com/vaskoz/dailycodingproblem-go/issues/676)
 * [Day 340](https://github.com/vaskoz/dailycodingproblem-go/issues/679)
+* [Day 342](https://github.com/vaskoz/dailycodingproblem-go/issues/682)

day342/problem.go

@@ -0,0 +1,14 @@
+package day342
+
+// Reduce is a function that takes in an array,
+// a combining function, and an initial value
+// and builds up a result by calling the combining
+// function on each element of the array, left to right.
+func Reduce(lst []interface{},
+	reducer func(a, b interface{}) interface{},
+	initial interface{}) interface{} {
+	for _, v := range lst {
+		initial = reducer(initial, v)
+	}
+	return initial
+}

day342/problem_test.go

@@ -0,0 +1,48 @@
+package day342
+
+import (
+	"fmt"
+	"testing"
+)
+
+// nolint
+var testcases = []struct {
+	lst      []interface{}
+	reducer  func(a, b interface{}) interface{}
+	initial  interface{}
+	expected interface{}
+}{
+	{
+		[]interface{}{1, 2, 3, 4, 5, 6},
+		func(a, b interface{}) interface{} {
+			return a.(int) + b.(int)
+		},
+		0,
+		21,
+	},
+	{
+		[]interface{}{"hello", "world", "goodbye"},
+		func(a, b interface{}) interface{} {
+			return fmt.Sprintf("%s %s", a, b)
+		},
+		"begin",
+		"begin hello world goodbye",
+	},
+}
+
+func TestReduce(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := Reduce(tc.lst, tc.reducer, tc.initial); result != tc.expected {
+			t.Errorf("Expected %v, got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkReduce(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			Reduce(tc.lst, tc.reducer, tc.initial)
+		}
+	}
+}