Your function should return length = 5, and A is now [1,1,2,2,3]

#include <iostream>

using namespace::std;

int removeDuplicates(int *A, int length){
    if(length<=2) return length;
    
    int n=2;
    for(int i=2; i < length; i++){
        // 判断只要有一个不相等 那么就不符合三连等的情况
        if(A[n-2]!=A[n-1] || A[n-2]!=A[i]){
            A[n++] = A[i];
        }
    }
    return n;
}

int main(int argc, const char * argv[])
{

    // insert code here...
    std::cout << "Hello, World!\n";
    
    int n = 17+1;
    int A[]={1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,3,3};
    int resu = removeDuplicates(A, n);
    for(int i=0; i < resu; i++)
        cout << A[i] << " ";
    return 0;
}

LeetCode Remove Duplicates from Sorted Array II