Remove Duplicates from Sorted Array Java Solution - The Coding Shala

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Remove Duplicates from Sorted Array

Problem:

Given sorted array nums, remove the duplicates in-place such that each element appears only once and returns 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.

Remove Duplicates from Sorted Array Java Solution

Approach 1:

We can use an extra array.

Time Complexity O(n)

Space Complexity O(n).

Java 

class Solution {
    public int removeDuplicates(int[] nums) {
       int[] ans = new int[nums.length];
        if(nums.length == 0) return 0;
        int j = 0;
        for(int i=0; i<nums.length-1;i++){
            if(nums[i]!=nums[i+1]){
                ans[j]=nums[i];
                j++;
            }
        }
        ans[j] = nums[nums.length-1];
        j++;
        for(int i=0;i<j;i++) nums[i] = ans[i];
        return j;
    }
}

Approach 2:

Use two pointers.

Time Complexity O(n)

Space Complexity O(1).

Java 

class Solution {
    public int removeDuplicates(int[] nums) {
        int i = 0;
        for(int j = 1; j< nums.length; j++){
           if(nums[i] != nums[j]) nums[++i] = nums[j]; 
        }
        return i+1;
    }
}

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