二分查找与三分查找算法 C#

首先是二分查找法，时间复杂度O（2log2（n））：

        static bool Find(int[] sortedArray, int number)
        {
            if (sortedArray.Length == 0)
                return false;

            int start = 0;
            int end = sortedArray.Length - 1;

            while (end >= start)
            {
                int middle = (start + end) / 2;
                if (sortedArray[middle] < number)
                    start = middle + 1;
                else if (sortedArray[middle] > number)
                    end = middle - 1;
                else
                    return true;
            }
            return false;
        }

然后是三分查找算法，时间复杂度O（3log3（n））：

       static bool Find(int[] sortedArray, int number)
        {
            if (sortedArray.Length == 0)
                return false;

            int start = 0;
            int end = sortedArray.Length - 1;

            while (end >= start)
            {
                int firstMiddle = (end - start) / 3 + start;
                int secondMiddle = end - (end - start) / 3;
                if (sortedArray[firstMiddle] > number)
                    end = firstMiddle - 1;
                else if (sortedArray[secondMiddle] < number)
                    start = secondMiddle + 1;
                else if (sortedArray[firstMiddle] != number && sortedArray[secondMiddle] != number)
                {
                    end = secondMiddle - 1;
                    start = firstMiddle + 1;
                }
                else
                    return true;
            }
            return false;
        }

对比可以发现，三分查找算法的时间复杂度要比二分查找算法的时间复杂度低，但是实际上效率并没有二分查找算法高，因此我们不能过于迷信一个算法的时间复杂度。