bulbs - facebook code lab - answer provided from the lab - standard and elegant one

bulb.cpp

class Solution {
    public:
	    int bulbs(vector<int> &A) {
		    int state= 0, ans = 0;
		    for (int i = 0;i < A.size();i++) {
			    if (A[i] == state) {
				    ans++;
				    state = 1 - state;
			    }
		    }
		    return ans;
	    }
};