二分法查找

import random


class Search(object):

    def binary_search(self, data, value):
        """
        二分查找迭代法实现
        :param data: list 待查找序列
        :param value: int 待查数据
        :return: int 索引（查找不到返回-1）
        """
        low = 0
        high = len(data) - 1
        while low <= high:
            mid = int((low + high) / 2)
            if value < data[mid]:
                high = mid - 1
            elif value > data[mid]:
                low = mid + 1
            else:
                return mid + 1
        return -1

    def binary_search_recursion(self, data, low, high, value):
        """
        二分查找递归法实现
        :param data: list 待查找序列
        :param low: int low指针
        :param high: int high指针
        :param value: int 待查数据
        :return: int 索引（查找不到返回-1）
        """
        if low <= high:
            mid = int((low + high) / 2)
            if value < data[mid]:
                return self.binary_search_recursion(data, low, mid - 1, value)
            elif value > data[mid]:
                return self.binary_search_recursion(data, mid + 1, high, value)
            else:
                return mid + 1
        return -1


def main():
    search = Search()
    data = [0] * 10
    for index in range(len(data)):
        data[index] = random.randint(1, 10)
    data = sorted(data)
    print("待查找序列：", data)
    res_index = search.binary_search_recursion(data, 0, len(data) - 1, 5)
    print("结果索引为：", res_index)
    res_index = search.binary_search(data, 5)
    print("结果索引为：", res_index)


if __name__ == '__main__':
    main()