build

docs/chapter_divide_and_conquer/binary_search_recur.md

@@ -422,9 +422,32 @@ comments: true
 === "Ruby"
 
     ```ruby title="binary_search_recur.rb"
-    [class]{}-[func]{dfs}
+    ### 二分查找：问题 f(i, j) ###
+    def dfs(nums, target, i, j)
+      # 若区间为空，代表无目标元素，则返回 -1
+      return -1 if i > j
+      
+      # 计算中点索引 m
+      m = (i + j) / 2
 
-    [class]{}-[func]{binary_search}
+      if nums[m] < target
+        # 递归子问题 f(m+1, j)
+        return dfs(nums, target, m + 1, j)
+      elsif nums[m] > target
+        # 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
+      end
+    end
+
+    ### 二分查找 ###
+    def binary_search(nums, target)
+      n = nums.length
+      # 求解问题 f(0, n-1)
+      dfs(nums, target, 0, n - 1)
+    end
     ```
 
 === "Zig"