class BinarySearch
    {
        /// <summary>
        /// 查詢方法
        /// </summary>
        /// <param name="nums">資料</param>
        /// <param name="target">目標值</param>
        /// <returns></returns>
        public int search(int[] nums, int target)
        {
            
 
int len = nums.Length;
            int left = 0;
            int right = len - 1;
            //目標元素可能存在在區間 [left, right]
            while (left <= right)
            {
                //推薦的寫法是 int mid = left + (right - left) / 2;
                int mid = (left + right) / 2;
                if (nums[mid] == target)
                {
                    
 
return mid;
                }
                //如果中間小於目標
                else if (nums[mid] < target)
                {
                    // 目標元素可能存在在區間 [mid + 1, right]
                    left = mid + 1;
                }
                //如果中間大於目標
                else
                {
                    
 
// 目標元素可能存在在區間 [left, mid - 1]
                    right = mid - 1;
                }
            }

            return -1;
        }
    }

在上圖解: