Remove Duplicates from Sorted Array

• leetcode 26
• Company: Microsoft, Bloomberg, Faceboook
• Hide Tags: Array, Two Pointers
• Similar Problems: Remove Element

Description

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 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 new length.

C++ solution

int removeDuplicates(vector<int>& nums){
    if(nums.empty()) return 0;
    int index = 0;
    for(int i = 1; i < nums.size(); i++){
      if(nums[index] != nums[i])
        nums[++index] = nums[i];
    }

    return index+1;
}

There is another similar c++ solution

int removeDuplicates(vector<int>& nums) {
      int count = 0;

      for(int i = 1; i < nums.size(); i++){
          if(nums[i] == nums[i-1]) count++;
          else nums[i - count] = nums[i];
      }
        return nums.size()-count;
 }

Java Solution

 public int removeDuplicates(int[] nums) {
        if(nums.length == 0) return 0;

        int index = 0;
        for(int i = 0; i < nums.length; i++){
            if(nums[i] != nums[index])
              nums[++index] = nums[i];
        }

        return index + 1;
    }

Post Thinking

The think is same, we use two index to record current position and new position. Indeed it is an two points problem.