chore: import upstream snapshot with attribution

2026-07-13 13:25:42 +08:00
commit 4e0f4422d0
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+Given an unsorted integer array nums.
+Return the smallest positive integer that is not present in nums.
+
+You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space.
+
+## Example 1:
+
+> Input: nums = [1,2,0]
+> Output: 3
+> Explanation: The numbers in the range [1,2] are all in the array.
+
+## Example 2:
+
+> Input: nums = [3,4,-1,1]
+> Output: 2
+> Explanation: 1 is in the array but 2 is missing.
+
+## Example 3:
+
+> Input: nums = [7,8,9,11,12]
+> Output: 1
+> Explanation: The smallest positive integer 1 is missing.
+
+## Constraints:
+
+1 <= nums.length <= 105
+-231 <= nums[i] <= 231 - 1
+