Remove duplicates from sorted array

Array Two Pointers

62.3% acceptance

Jan 12, 2026

18819

20480

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Consider the number of unique elements in nums to be k. After removing duplicates, return the number of unique elements k. The first k elements of nums should contain the unique numbers in sorted order. The remaining elements beyond index k - 1 can be ignored. Custom Judge: The judge will test your solution with the following code: int[] nums = [...]; // Input array int[] expectedNums = [...]; // The expected answer with correct length int k = removeDuplicates(nums); // Calls your implementation assert k == expectedNums.length; for (int i = 0; i < k; i++) { assert nums[i] == expectedNums[i]; } If all assertions pass, then your solution will be accepted.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn remove_duplicates(nums: &mut Vec<i32>) -> i32 {
    if nums.is_empty() {
      return 0;
    }
    
    let mut write_index = 1;
    
    for read_index in 1..nums.len() {
      if nums[read_index] != nums[write_index - 1] {
        nums[write_index] = nums[read_index];
        write_index += 1;
      }
    }
    
    write_index as i32
  }
}