feat: Add Go code to binary search recursion under divide and conquer (#630)

* feat: Add Go code to binary search recursion under divide and conquer

* style: Code comment standardization

* style: modify function comment

codes/go/chapter_divide_and_conquer/binary_search_recur.go

@@ -0,0 +1,34 @@
+// File: binary_search_recur.go
+// Created Time: 2023-07-19
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+/* 二分查找：问题 f(i, j) */
+func dfs(nums []int, target, i, j int) int {
+	// 如果区间为空，代表没有目标元素，则返回 -1
+	if i > j {
+		return -1
+	}
+	//	计算索引中点
+	m := i + ((j - i) >> 1)
+	//判断中点与目标元素大小
+	if nums[m] < target {
+		// 小于则递归右半数组
+		// 递归子问题 f(m+1, j)
+		return dfs(nums, target, m+1, j)
+	} else if nums[m] > target {
+		// 小于则递归左半数组
+		// 递归子问题 f(i, m-1)
+		return dfs(nums, target, i, m-1)
+	} else {
+		// 找到目标元素，返回其索引
+		return m
+	}
+}
+
+/* 二分查找 */
+func binarySearch(nums []int, target int) int {
+	n := len(nums)
+	return dfs(nums, target, 0, n-1)
+}

codes/go/chapter_divide_and_conquer/binary_search_recur_test.go

@@ -0,0 +1,20 @@
+// File: binary_search_recur_test.go
+// Created Time: 2023-07-19
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestBinarySearch(t *testing.T) {
+	nums := []int{1, 3, 6, 8, 12, 15, 23, 26, 31, 35}
+	target := 6
+	noTarget := 99
+	targetIndex := binarySearch(nums, target)
+	fmt.Println("目标元素 6 的索引 = ", targetIndex)
+	noTargetIndex := binarySearch(nums, noTarget)
+	fmt.Println("不存在目标元素的索引 = ", noTargetIndex)
+}