LeetCode Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":

What if duplicates are allowed at most twice?

For example,

Given sorted array A = 

[1,1,1,2,2,3]

,

Your function should return length = 

5

, and A is now 

[1,1,2,2,3]

.

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