mirror of
https://github.com/krahets/hello-algo.git
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e720aa2d24
* Sync recent changes to the revised Word. * Revised the preface chapter * Revised the introduction chapter * Revised the computation complexity chapter * Revised the chapter data structure * Revised the chapter array and linked list * Revised the chapter stack and queue * Revised the chapter hashing * Revised the chapter tree * Revised the chapter heap * Revised the chapter graph * Revised the chapter searching * Reivised the sorting chapter * Revised the divide and conquer chapter * Revised the chapter backtacking * Revised the DP chapter * Revised the greedy chapter * Revised the appendix chapter * Revised the preface chapter doubly * Revised the figures
100 lines
2.6 KiB
Python
100 lines
2.6 KiB
Python
"""
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File: array.py
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Created Time: 2022-11-25
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Author: Krahets (krahets@163.com)
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"""
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import random
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def random_access(nums: list[int]) -> int:
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"""随机访问元素"""
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# 在区间 [0, len(nums)-1] 中随机抽取一个数字
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random_index = random.randint(0, len(nums) - 1)
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# 获取并返回随机元素
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random_num = nums[random_index]
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return random_num
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# 请注意，Python 的 list 是动态数组，可以直接扩展
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# 为了方便学习，本函数将 list 看作长度不可变的数组
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def extend(nums: list[int], enlarge: int) -> list[int]:
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"""扩展数组长度"""
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# 初始化一个扩展长度后的数组
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res = [0] * (len(nums) + enlarge)
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# 将原数组中的所有元素复制到新数组
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for i in range(len(nums)):
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res[i] = nums[i]
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# 返回扩展后的新数组
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return res
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def insert(nums: list[int], num: int, index: int):
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"""在数组的索引 index 处插入元素 num"""
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# 把索引 index 以及之后的所有元素向后移动一位
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for i in range(len(nums) - 1, index, -1):
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nums[i] = nums[i - 1]
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# 将 num 赋给 index 处的元素
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nums[index] = num
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def remove(nums: list[int], index: int):
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"""删除索引 index 处的元素"""
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# 把索引 index 之后的所有元素向前移动一位
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for i in range(index, len(nums) - 1):
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nums[i] = nums[i + 1]
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def traverse(nums: list[int]):
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"""遍历数组"""
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count = 0
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# 通过索引遍历数组
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for i in range(len(nums)):
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count += nums[i]
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# 直接遍历数组元素
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for num in nums:
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count += num
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# 同时遍历数据索引和元素
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for i, num in enumerate(nums):
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count += nums[i]
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count += num
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def find(nums: list[int], target: int) -> int:
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"""在数组中查找指定元素"""
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for i in range(len(nums)):
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if nums[i] == target:
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return i
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return -1
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"""Driver Code"""
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if __name__ == "__main__":
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# 初始化数组
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arr = [0] * 5
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print("数组 arr =", arr)
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nums = [1, 3, 2, 5, 4]
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print("数组 nums =", nums)
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# 随机访问
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random_num: int = random_access(nums)
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print("在 nums 中获取随机元素", random_num)
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# 长度扩展
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nums: list[int] = extend(nums, 3)
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print("将数组长度扩展至 8 ，得到 nums =", nums)
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# 插入元素
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insert(nums, 6, 3)
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print("在索引 3 处插入数字 6 ，得到 nums =", nums)
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# 删除元素
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remove(nums, 2)
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print("删除索引 2 处的元素，得到 nums =", nums)
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# 遍历数组
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traverse(nums)
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# 查找元素
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index: int = find(nums, 3)
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print("在 nums 中查找元素 3 ，得到索引 =", index)
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