Remove Duplicates from Sorted Array Solutions in C++

// Source : https://oj.leetcode.com/problems/remove-duplicates-from-sorted-array/
// Author : Hao Chen
// Date   : 2014-06-22



class Solution {
public:
    int removeDuplicates(int A[], int n) {
        
        if (n<=1) return n;
        
        int pos=0;
        for(int i=0; i<n-1; i++){
            if (A[i]!=A[i+1]){
                A[++pos] = A[i+1];
            }
        }
        return pos+1;
    }
};

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        if (n < 2) return n;
        int size = 1;
        for (int i = 1; i != n; ++i)
            if (A[i-1] != A[i])
                A[size++] = A[i];
        return size;
    }
};

/// Source : https://leetcode.com/problems/remove-duplicates-from-sorted-array/
/// Author : liuyubobobo
/// Time   : 2016-12-06


#include <iostream>
#include <vector>
#include <cassert>
#include <stdexcept>

using namespace std;

/// Two pointers
/// Time Complexity:  O(n)
/// Space Complexity: O(1)
class Solution {
public:
    int removeDuplicates(vector<int>& nums) {

        if(nums.size() == 0)
            return 0;

        int res = 1;
        int index = nextDifferentCharacterIndex(nums, 1);
        int i = 1;
        while(index < nums.size()){
            res ++;
            nums[i++] = nums[index];
            index = nextDifferentCharacterIndex(nums, index + 1);
        }

        return res;
    }

private:
    int nextDifferentCharacterIndex(const vector<int> &nums, int p){
        for( ; p < nums.size() ; p ++ )
            if( nums[p] != nums[p - 1] )
                break;
        return p;
    }
};


int main() {

    vector<int> nums1 = {1, 1, 2};
    cout << Solution().removeDuplicates(nums1) << endl;

    return 0;
}