Leetcode 26. delete duplicates in the ordered array

Power button | 26. Remove duplicate items from an ordered array

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Be careful ： The topic requires that no extra space be occupied , It is not allowed to modify the input array in place .

Method ： Double finger needling

Ideas ： Compare the elements in the array with each other , If you find duplicates, delete . But this method is generally applicable to creating a new empty array , Put every non repeating element into it . If you modify it directly in the original array , Misoperation may occur . Better think in reverse . Use two cursors to indicate , A cursor is responsible for recording changes , The other is for comparison . Compare the cursors. If the values before and after are different, use the recording cursor to record . This ensures that the new array will not have duplicate options . Return the recorded value .

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        if not nums:
            return 0

        n = len(nums)
        i = 1
        j = 1
        while j < n:
            if nums[j] != nums[j - 1]:
                nums[i] = nums[j]
                i += 1
            j += 1

        return i

if __name__ == "__main__":
    a = Solution()
    nums = [1, 1, 2]
    print(a.removeDuplicates(nums))