Merge pull request #96 from scissorsfeet/master

15_binarysearch by golang

go/15_binarysearch/binarysearch.go

@@ -0,0 +1,47 @@
+package _5_binarysearch
+
+func BinarySearch(a []int, v int) int {
+	n := len(a)
+	if n == 0 {
+		return -1
+	}
+
+	low := 0
+	high := n - 1
+	for low <= high {
+		mid := (low + high) / 2
+		if a[mid] == v {
+			return mid
+		} else if a[mid] > v {
+			high = mid - 1
+		} else {
+			low = mid + 1
+		}
+	}
+
+	return -1
+}
+
+func BinarySearchRecursive(a []int, v int) int {
+	n := len(a)
+	if n == 0 {
+		return -1
+	}
+
+	return bs(a, v, 0, n-1)
+}
+
+func bs(a []int, v int, low, high int) int {
+	if low > high {
+		return -1
+	}
+
+	mid := (low + high) / 2
+	if a[mid] == v {
+		return mid
+	} else if a[mid] > v {
+		return bs(a, v, low, mid-1)
+	} else {
+		return bs(a, v, mid+1, high)
+	}
+}

go/15_binarysearch/binarysearch_test.go

@@ -0,0 +1,27 @@
+package _5_binarysearch
+
+import "testing"
+
+func TestBinarySearch(t *testing.T) {
+	var a []int
+
+	a = []int{1, 3, 5, 6, 8}
+	if BinarySearch(a, 8) != 4 {
+		t.Fatal(BinarySearch(a, 3))
+	}
+	if BinarySearch(a, 4) != -1 {
+		t.Fatal(BinarySearch(a, 4))
+	}
+}
+
+func TestBinarySearchRecursive(t *testing.T) {
+	var a []int
+
+	a = []int{1, 3, 5, 6, 8}
+	if BinarySearchRecursive(a, 8) != 4 {
+		t.Fatal(BinarySearch(a, 3))
+	}
+	if BinarySearchRecursive(a, 4) != -1 {
+		t.Fatal(BinarySearch(a, 4))
+	}
+}