Given a sorted array, 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 in place with constant memory. For example, Given input array A = [1,1,2], Your function should return length = 2, and A is now [1,2].

Remove Duplicates from Sorted Array.java

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

Hi, if I try to solve the problem in C. I need a variable to store the length of the array. Is it against the subject's rule?

@Manuel4131, no, because that counts as constant memory. Regardless of array size, you'll only need the one variable to store its length.

Your solution is not correct, will fail for say [0,0,0,1,1]

class Solution {
public int removeDuplicates(int[] nums) {
int i=0, j=0;
int dup=0; // number of duplicates in nums[]
while (j+1 < nums.length){
if (nums[j] == nums[j+1]){
j++;
dup++;
}else{
j++;
nums[++i] = nums[j];
}
}
return nums.length - dup;
}
}