写了二分查找算法,欢迎查找算法bug

 

刚才看了《只有10%程序员能正确实现二分查找算法》文章http://news.csdn.net/a/20100423/218099.html,于是忍不住用C#写了个,欢迎查找算法的bug

 

二分查找可以解决(预排序数组的查找)问题:只要数组中包含T(即要查找的值),那么通过不断缩小包含T的范围,最终就可以找到它。一开始,范围覆盖整个数组。将数组的中间项与T进行比较,可以排除一半元素,范围缩小一半。就这样反复比较,反复缩小范围,最终就会在数组中找到T,或者确定原以为T所在的范围实际为空。对于包含N个元素的表,整个查找过程大约要经过log(2)N次比较。

 

/// <summary>
        /// 二分查找法
        /// </summary>
        /// <param name="aa"></param>
        /// <param name="a"></param>
        /// <returns></returns>
        public static int GetPosition(int[] aa, int a)
        {

            int arrLength = aa.Length;
            int startPosition = 0;
            int endPosition = arrLength - 1;
            int middlePosition = endPosition / 2;

            if (arrLength>0)
            {
                return GetValuePosition(aa, a, startPosition, endPosition, middlePosition);
            }

            return -1;

        }

        public static  int GetValuePosition(int[] aa,int a,int startPosition,int endPosition,int middlePosition)
        {
            if (a == aa[middlePosition])
            {
                return middlePosition;
            }
            if (a > aa[middlePosition]&&endPosition>=startPosition)
            {
                startPosition = middlePosition + 1;
                middlePosition = (endPosition + startPosition) / 2;
               return GetValuePosition(aa, a, startPosition, endPosition, middlePosition);

            }
            else if(a<aa[middlePosition]&&endPosition>=startPosition)
            {
                endPosition = middlePosition - 1;
                middlePosition = (endPosition + startPosition) / 2;
               return  GetValuePosition(aa, a, startPosition, endPosition, middlePosition);
            }

            return -1;

        }

 

作者:边写边唱

文章出处:http://www.cnblogs.com/zoupeiyang

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posted on 2010-04-24 11:26  边写边唱  阅读(521)  评论(1编辑  收藏  举报

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