Update iterBinarySearch and add tests (#247)

Co-authored-by: Rak Laptudirm <[email protected]>

Author: Crazy3lf

search/binary.go

@@ -1,38 +1,38 @@
 package search
 
-// Binary Binary Search
-func Binary(array []int, target int, lowIndex int, highIndex int) int {
+// Binary search for target within a sorted array by repeatedly dividing the array in half and comparing the midpoint with the target.
+// This function uses recursive call to itself.
+// If a target is found, the index of the target is returned. Else the function return -1 and ErrNotFound.
+func Binary(array []int, target int, lowIndex int, highIndex int) (int, error) {
 	if highIndex < lowIndex || len(array) == 0 {
-		return -1
+		return -1, ErrNotFound
 	}
-	mid := (highIndex + lowIndex) / 2
+	mid := int(lowIndex + (highIndex-lowIndex)/2)
 	if array[mid] > target {
 		return Binary(array, target, lowIndex, mid-1)
 	} else if array[mid] < target {
 		return Binary(array, target, mid+1, highIndex)
 	} else {
-		return mid
+		return mid, nil
 	}
 }
 
-// BinaryIterative Iterative Binary Search
-func BinaryIterative(array []int, target int, lowIndex int, highIndex int) int {
+// BinaryIterative search for target within a sorted array by repeatedly dividing the array in half and comparing the midpoint with the target.
+// Unlike Binary, this function uses iterative method and not recursive.
+// If a target is found, the index of the target is returned. Else the function return -1 and ErrNotFound.
+func BinaryIterative(array []int, target int, lowIndex int, highIndex int) (int, error) {
 	startIndex := lowIndex
 	endIndex := highIndex
 	var mid int
-	size := len(array)
-	if size == 0 || highIndex > size || lowIndex < 0 {
-		return -1
-	}
 	for startIndex <= endIndex {
-		mid = (endIndex + startIndex) / 2
+		mid = int(startIndex + (endIndex-startIndex)/2)
 		if array[mid] > target {
 			endIndex = mid - 1
 		} else if array[mid] < target {
 			startIndex = mid + 1
 		} else {
-			return mid
+			return mid, nil
 		}
 	}
-	return -1
+	return -1, ErrNotFound
 }

search/binary_test.go

@@ -1,23 +1,51 @@
 package search
 
-import (
-	"testing"
-)
+import "testing"
 
 func TestBinarySearch(t *testing.T) {
 	for _, test := range searchTests {
-		actual := Binary(test.data, test.key, 0, len(test.data)-1)
-		if actual != test.expected {
-			t.Errorf("test %s failed", test.name)
+		actualValue, actualError := Binary(test.data, test.key, 0, len(test.data)-1)
+		if actualValue != test.expected {
+			t.Errorf("test '%s' failed: input array '%v' with key '%d', expected '%d', get '%d'", test.name, test.data, test.key, test.expected, actualValue)
+		}
+		if actualError != test.expectedError {
+			t.Errorf("test '%s' failed: input array '%v' with key '%d', expected error '%s', get error '%s'", test.name, test.data, test.key, test.expectedError, actualError)
 		}
 	}
 }
 
 func TestIterBinarySearch(t *testing.T) {
 	for _, test := range searchTests {
-		actual := BinaryIterative(test.data, test.key, 0, len(test.data)-1)
-		if actual != test.expected {
-			t.Errorf("test %s failed", test.name)
+		actualValue, actualError := BinaryIterative(test.data, test.key, 0, len(test.data)-1)
+		if actualValue != test.expected {
+			t.Errorf("test '%s' failed: input array '%v' with key '%d', expected '%d', get '%d'", test.name, test.data, test.key, test.expected, actualValue)
+		}
+		if actualError != test.expectedError {
+			t.Errorf("test '%s' failed: input array '%v' with key '%d', expected error '%s', get error '%s'", test.name, test.data, test.key, test.expectedError, actualError)
 		}
 	}
 }
+
+func generateBenchmarkTestCase() []int {
+	var testCase []int
+	for i := 0; i < 100; i++ {
+		testCase = append(testCase, i)
+	}
+	return testCase
+}
+
+func BenchmarkBinarySearch(b *testing.B) {
+	testCase := generateBenchmarkTestCase()
+	b.ResetTimer() // this is important because the generateBenchmarkTestCase() is expensive
+	for i := 0; i < b.N; i++ {
+		_, _ = Binary(testCase, 10, 0, len(testCase)-1)
+	}
+}
+
+func BenchmarkIterBinarySearch(b *testing.B) {
+	testCase := generateBenchmarkTestCase()
+	b.ResetTimer() // this is important because the generateBenchmarkTestCase() is expensive
+	for i := 0; i < b.N; i++ {
+		_, _ = BinaryIterative(testCase, 10, 0, len(testCase)-1)
+	}
+}

search/errors.go

@@ -0,0 +1,6 @@
+package search
+
+import "errors"
+
+// ErrNotFound is returned by search functions when target is not found
+var ErrNotFound = errors.New("target not found in array")

search/testcases.go

@@ -1,22 +1,30 @@
 package search
 
 type searchTest struct {
-	data     []int
-	key      int
-	expected int
-	name     string
+	data          []int
+	key           int
+	expected      int
+	expectedError error
+	name          string
 }
 
 // Note that these are immutable therefore they are shared among all the search tests.
 // If your algorithm is mutating these then it is advisable to create separate test cases.
 var searchTests = []searchTest{
 	//Sanity
-	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 1, 0, "Sanity"},
-	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 5, 4, "Sanity"},
-	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 10, 9, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 10, 9, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 9, 8, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 8, 7, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 7, 6, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 6, 5, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 5, 4, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 4, 3, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 3, 2, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 2, 1, nil, "Sanity"},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 1, 0, nil, "Sanity"},
 	//Absent
-	{[]int{1, 4, 5, 6, 7, 10}, -25, -1, "Absent"},
-	{[]int{1, 4, 5, 6, 7, 10}, 25, -1, "Absent"},
+	{[]int{1, 4, 5, 6, 7, 10}, -25, -1, ErrNotFound, "Absent"},
+	{[]int{1, 4, 5, 6, 7, 10}, 25, -1, ErrNotFound, "Absent"},
 	//Empty slice
-	{[]int{}, 2, -1, "Empty"},
+	{[]int{}, 2, -1, ErrNotFound, "Empty"},
 }