【672. 灯泡开关 Ⅱ】状态空间缩小

//只需要考虑前6位的状态，i这种状态和i+6这个状态是一样的

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.HashSet;

class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        System.out.println(solution.flipLights(3,2));
    }
    public int flipLights(int n, int presses) {
        n = Math.min(n,6);
        char[] arr = new char[n];
        for (int i = 0; i < n; i++) {
            arr[i] = '1';
        }
        ArrayDeque<char[]> deque = new ArrayDeque<>();
        deque.add(arr);
        int step = 0;
        while (!deque.isEmpty() && step <  presses) {
            ArrayDeque<char[]> nextDeque = new ArrayDeque<>();
            step++;
            HashSet<String> set = new HashSet<>();
            while(!deque.isEmpty()){
                char[] state = deque.poll();

                char[] newState = new char[n];
                for (int i = 0; i < n; i++) {
                    newState[i] = state[i] == '1' ? '0' : '1';
                }
                if (!set.contains(new String(newState))) {
                    set.add(new String(newState));
                    nextDeque.offer(Arrays.copyOf(newState,n));
                }
                for (int i = 0; i < n; i++) {
                    if (i % 2 == 1) {
                        newState[i] = state[i];
                    } else {
                        newState[i] = state[i] == '1' ? '0' : '1';
                    }
                }
                if (!set.contains(new String(newState))) {
                    set.add(new String(newState));
                    nextDeque.offer(Arrays.copyOf(newState,n));
                }
                for (int i = 0; i < n; i++) {
                    if (i % 2 == 0) {
                        newState[i] = state[i];
                    } else {
                        newState[i] = state[i] == '1' ? '0' : '1';
                    }
                }
                if (!set.contains(new String(newState))) {
                    set.add(new String(newState));
                    nextDeque.offer(Arrays.copyOf(newState,n));
                }
                for (int i = 1; i <= n; i++) {
                    if (i % 3 != 1) {
                        newState[i - 1] = newState[i - 1];
                    } else {
                        newState[i - 1] = newState[i - 1] == '1' ? '0' : '1';
                    }
                }
                if (!set.contains(new String(newState))) {
                    set.add(new String(newState));
                    nextDeque.offer(Arrays.copyOf(newState,n));
                }
            }
            deque = nextDeque;
        }
        return deque.size();
    }



}