leetcode Remove Duplicates from Sorted Array II

/*****************************************************************
created:    2014/09/13 16:16
filename:    remove-duplicates-from-sorted-array.cpp
author:        Justme0 (http://blog.csdn.net/justme0)

purpose:    有序数组中，有至少三个相同元素时删掉只留两个
https://oj.leetcode.com/problems/remove-duplicates-from-sorted-array-ii/
*****************************************************************/

#include <iostream>
#include <cassert>
#include <vector>
using namespace std;

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        if (n <= 2) {
            return n;
        }

        vector<int> iVec;
        iVec.push_back(A[0]);
        for (int i = 1; i < n - 1; ++i) {
            if (!(A[i - 1] == A[i] && A[i] == A[i + 1])) {
                iVec.push_back(A[i]);
            }
        }
        iVec.push_back(A[n - 1]);

        assert(iVec.size() <= unsigned(n));
        for (unsigned i = 0; i < iVec.size(); ++i) {
            A[i] = iVec[i];
        }

        return iVec.size();
    }
};

class Solution2 {
public:
    int removeDuplicates(int A[], int n) {
        if (n <= 2) {
            return n;
        }

        int len = 2;
        for (int i = 2; i < n; ++i) {
            if (A[i] != A[len - 2]) {
                A[len] = A[i];
                ++len;
            }
        }
        assert(len <= n);

        return len;
    }
};

int main(int argc, char **argv) {
    int arr[] = {1, 1, 2, 2, 3};
    int len = sizeof arr / sizeof *arr;
    int new_len = Solution2().removeDuplicates(arr, len);
    for (int i = 0; i < new_len; ++i) {
        cout << arr[i] << endl;
    }

    system("PAUSE");
    return 0;
}