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Remove Duplicates from Sorted Array

Given a sorted array nums, remove the duplicates in-place such that each element appear only once 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.

Example 1:

Given nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively.

It doesn't matter what you leave beyond the returned length.

Example 2:

Given nums = [0,0,1,1,1,2,2,3,3,4],

Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively.

It doesn't matter what values are set beyond the returned length.

Solution

/**
 * @param {number[]} nums
 * @return {number}
 * @time complexity: O(n)
 * @space complexity: O(1)
 */

function removeDuplicates(nums) {
  let i = 0;

  for (let j = 1; j < nums.length; j++) {
    if (nums[j] !== nums[i]) {
      i++;
      nums[i] = nums[j];
    }
  }

  nums.splice(i+1, nums.length - i);

  return i + 1;
};

Alternative Solution

/**
 * @param {number[]} nums
 * @return {number}
 * @time complexity: O(n)
 * @space complexity: O(1)
 */
function removeDuplicates(nums) {
  for (let i = 0; i < nums.length-1; i++) {
    if (nums[i] === nums[i+1]) {
      nums.splice(i, 1);
      i--;
    }
  }
  return nums.length;
}

Test Case

const assert = require('chai').assert;

describe('Remove Duplicates from Sorted Array', () => {

  it('should return [1, 2]', () => {
    const nums = [1, 1, 2];
    const result = removeDuplicates(nums);

    assert.deepEqual(nums, [1, 2]);
    assert.strictEqual(result, 2);
  });

  it('should return [0, 1, 2, 3, 4]', () => {
    const nums = [0,0,1,1,1,2,2,3,3,4];
    const result = removeDuplicates(nums);

    assert.deepEqual(nums, [0, 1, 2, 3, 4]);
    assert.strictEqual(result, 5);
  });

});
  Remove Duplicates from Sorted Array
    ✓ should return [1, 2]
    ✓ should return [0, 1, 2, 3, 4]


  2 passing (15ms)


Mike Mai
Mike Mai   Brooklyn, New York
I am a full-stack web developer. I love to learn cutting-edge technology and solve problems. I also like photography and graphic designs.