diff --git a/codes/python/chapter_searching/binary_search.py b/codes/python/chapter_searching/binary_search.py index 709a2b698..915573f62 100644 --- a/codes/python/chapter_searching/binary_search.py +++ b/codes/python/chapter_searching/binary_search.py @@ -1,10 +1,52 @@ ''' File: binary_search.py -Created Time: 2022-11-25 -Author: Krahets (krahets@163.com) +Created Time: 2022-11-26 +Author: timi (xisunyy@163.com) ''' import sys, os.path as osp + sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__)))) from include import * +""" 二分查找(双闭区间) """ +def binary_search(nums, target): + # 初始化双闭区间 [0, n-1] ,即 i, j 分别指向数组首元素、尾元素 + i, j = 0, len(nums) - 1 + while i <= j: + m = (i + j) // 2 # 计算中点索引 m + if nums[m] < target: # 此情况说明 target 在区间 [m+1, j] 中 + i = m + 1 + elif nums[m] > target: # 此情况说明 target 在区间 [i, m-1] 中 + j = m - 1 + else: + return m # 找到目标元素,返回其索引 + return -1 # 未找到目标元素,返回 -1 + + +""" 二分查找(左闭右开) """ +def binary_search1(nums, target): + # 初始化左闭右开 [0, n) ,即 i, j 分别指向数组首元素、尾元素+1 + i, j = 0, len(nums) + # 循环,当搜索区间为空时跳出(当 i = j 时为空) + while i < j: + m = (i + j) // 2 # 计算中点索引 m + if nums[m] < target: # 此情况说明 target 在区间 [m+1, j) 中 + i = m + 1 + elif nums[m] > target: # 此情况说明 target 在区间 [i, m) 中 + j = m + else: # 找到目标元素,返回其索引 + return m + return -1 # 未找到目标元素,返回 -1 + + +if __name__ == '__main__': + target = 6 + nums = [1, 3, 6, 8, 12, 15, 23, 67, 70, 92] + + # 二分查找(双闭区间) + index = binary_search(nums, target) + print("目标元素 6 的索引 = ", index) + # 二分查找(左闭右开) + index = binary_search1(nums, target) + print("目标元素 6 的索引 = ", index)