LeetCode 80: Remove Duplicates from Sorted Array II Solution

Master LeetCode problem 80 (Remove Duplicates from Sorted Array II), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

80. Remove Duplicates from Sorted Array II

Medium

Array Two Pointers

Problem Explanation

Explanation

To solve this problem, we will use two pointers approach. We will maintain a current pointer and a count variable to keep track of the number of occurrences of the current element. If the current element is the same as the previous element, we increment the count. If the count is less than or equal to 2, we copy the current element to the correct position in the array. If the count exceeds 2, we move the current pointer to the next element, effectively skipping over the duplicates. At the end, the current pointer will give us the final length of the array.

Time complexity: O(n) where n is the length of the input array nums.
Space complexity: O(1)

Solution Code

class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums.length <= 2) {
            return nums.length;
        }
        
        int current = 2;
        for(int i = 2; i < nums.length; i++) {
            if(nums[i] != nums[current-2]) {
                nums[current] = nums[i];
                current++;
            }
        }
        
        return current;
    }
}

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