Given K = 2^a[0] + 2^a[1] + ... + 2^a[n-1] calculate number of set bits in K*3

BitsInK3.java

public class BitsInK3 {
    static int solution(int A[]) {

        State state = new State();

        for (int i : A) {
            state.putBit(i);
            state.putBit(i + 1);
        }

        return state.getResult();
    }

    private static class State {
        int setBits = 0;
        int lastSetBit = -1;
        int lastBit = -1;

        void putBit(int i) {
            if (lastBit < i) {
                lastBit = i;
                lastSetBit = lastBit;
                setBits++;
            } else if (lastBit == i) {
                lastBit++;
            } else {
                setBits++;
            }
        }

        public int getResult() {
            return setBits;
        }
    }
}