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
52 lines
1.9 KiB
Python
52 lines
1.9 KiB
Python
"""
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File: binary_search.py
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Created Time: 2022-11-26
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Author: timi (xisunyy@163.com)
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"""
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def binary_search(nums: list[int], target: int) -> int:
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"""二分查找（双闭区间）"""
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# 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
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i, j = 0, len(nums) - 1
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# 循环，当搜索区间为空时跳出（当 i > j 时为空）
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while i <= j:
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# 理论上 Python 的数字可以无限大（取决于内存大小），无须考虑大数越界问题
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m = (i + j) // 2 # 计算中点索引 m
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if nums[m] < target:
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i = m + 1 # 此情况说明 target 在区间 [m+1, j] 中
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elif nums[m] > target:
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j = m - 1 # 此情况说明 target 在区间 [i, m-1] 中
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else:
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return m # 找到目标元素，返回其索引
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return -1 # 未找到目标元素，返回 -1
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def binary_search_lcro(nums: list[int], target: int) -> int:
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"""二分查找（左闭右开区间）"""
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# 初始化左闭右开区间 [0, n) ，即 i, j 分别指向数组首元素、尾元素+1
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i, j = 0, len(nums)
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# 循环，当搜索区间为空时跳出（当 i = j 时为空）
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while i < j:
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m = (i + j) // 2 # 计算中点索引 m
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if nums[m] < target:
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i = m + 1 # 此情况说明 target 在区间 [m+1, j) 中
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elif nums[m] > target:
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j = m # 此情况说明 target 在区间 [i, m) 中
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else:
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return m # 找到目标元素，返回其索引
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return -1 # 未找到目标元素，返回 -1
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"""Driver Code"""
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if __name__ == "__main__":
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target = 6
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nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
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# 二分查找（双闭区间）
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index: int = binary_search(nums, target)
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print("目标元素 6 的索引 = ", index)
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# 二分查找（左闭右开区间）
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index: int = binary_search_lcro(nums, target)
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print("目标元素 6 的索引 = ", index)
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