80. Remove Duplicates from Sorted Array II

Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most twice and return the new length.

Do not allocate extra space for another array; you must do this by modifying the input array in-place with O(1) extra memory.

Clarification:

Confused why the returned value is an integer, but your answer is an array?

Note that the input array is passed in by reference, which means a modification to the input array will be known to the caller.

Internally you can think of this:

// nums is passed in by reference. (i.e., without making a copy)
int len = removeDuplicates(nums);

// any modification to nums in your function would be known by the caller.
// using the length returned by your function, it prints the first len elements.
for (int i = 0; i < len; i++) {
    print(nums[i]);
}

 

Example 1:

Input: nums = [1,1,1,2,2,3]
Output: 5, nums = [1,1,2,2,3]
Explanation: Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3 respectively. It doesn't matter what you leave beyond the returned length.

Example 2:

Input: nums = [0,0,1,1,1,1,2,3,3]
Output: 7, nums = [0,0,1,1,2,3,3]
Explanation: Your function should return length = 7, with the first seven elements of nums being modified to 0, 0, 1, 1, 2, 3 and 3 respectively. It doesn't matter what values are set beyond the returned length.

 

Constraints:

  • 1 <= nums.length <= 3 * 104
  • -104 <= nums[i] <= 104
  • nums is sorted in ascending order.

Rust Solution

struct Solution;

impl Solution {
    fn remove_duplicates(nums: &mut Vec<i32>) -> i32 {
        let n = nums.len();
        let mut m = 0;
        let mut prev: Option<(i32, usize)> = None;
        for i in 0..n {
            if let Some((value, count)) = prev {
                if value == nums[i] {
                    if count == 1 {
                        prev = Some((nums[i], 2));
                        nums[m] = nums[i];
                        m += 1;
                    }
                } else {
                    prev = Some((nums[i], 1));
                    nums[m] = nums[i];
                    m += 1;
                }
            } else {
                prev = Some((nums[i], 1));
                nums[m] = nums[i];
                m += 1;
            }
        }
        m as i32
    }
}

#[test]
fn test() {
    let mut nums = vec![1, 1, 1, 2, 2, 3];
    let res = 5;
    assert_eq!(Solution::remove_duplicates(&mut nums), res);
}

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