37 lines
1.0 KiB
Markdown
37 lines
1.0 KiB
Markdown
# 数组
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## 二分
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```python
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def binary_search(nums, target):
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left, right = 0, len(nums) - 1
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while left <= right:
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mid = left + (right - left) // 2 # 防止溢出
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if nums[mid] == target:
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return mid # 找到目标，返回索引
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elif nums[mid] < target:
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left = mid + 1 # 目标在右半部分
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else:
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right = mid - 1 # 目标在左半部分
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return -1 # 未找到目标
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# 左右边界
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def left_bound(nums, target):
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left, right = 0, len(nums) - 1
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while left <= right:
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mid = left + (right - left) // 2
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if nums[mid] < target:
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left = mid + 1
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else:
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right = mid - 1
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return left if left < len(nums) and nums[left] == target else -1
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def right_bound(nums, target):
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left, right = 0, len(nums) - 1
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while left <= right:
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mid = left + (right - left) // 2
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if nums[mid] <= target:
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left = mid + 1
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else:
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right = mid - 1
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return right if right >= 0 and nums[right] == target else -1
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```
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