经典算法之查找

二分查找

  public class BinarySearch
    {
        public static int Search(List<int> list,int key)
        {
            int low = 0;
            int high = list.Count - 1;

            while (low <= high)
            {
                var middle = (low + high) / 2;
                
                if (list[middle] == key)
                    return middle;

                //如果中间值大于key
                if (list[middle] > key)
                    high = middle - 1;
                else
                    low = middle + 1;
            }
            return -1;
        }
    }

二：哈希查找

  /// <summary>
    /// 哈希函数
    /// </summary>
    public class HashSearch
    {
        static void InsertHash(int[] hash, int hashLength, int data)
        {   
            //哈希函数
            int hashAddress = data % 13;

            //如果key存在，则说明已经被占用,此时必须解决冲突
            while (hash[hashAddress] != 0)
            {   
                //用开放寻址法找到
                hashAddress = (++hashAddress) % hashLength;
            }
            hash[hashAddress] = data;
        }

        static int SearchHash(int[] hash, int hashLengh, int key)
        {   
            //哈希函数
            int hashAddress = key % hashLengh;

            while (hash[hashAddress] != 0 && hash[hashAddress] != key)
            {
                hashAddress = (++hashAddress) % hashLengh;
            }
            if (hash[hashAddress] == 0)
                return -1;
            return hashAddress;
        }
    }