957. Prison Cells After N Days

There are 8 prison cells in a row and each cell is either occupied or vacant.

Each day, whether the cell is occupied or vacant changes according to the following rules:

• If a cell has two adjacent neighbors that are both occupied or both vacant, then the cell becomes occupied.
• Otherwise, it becomes vacant.

Note that because the prison is a row, the first and the last cells in the row can’t have two adjacent neighbors.

You are given an integer array cells where cells[i] == 1 if the ith cell is occupied and cells[i] == 0 if the ith cell is vacant, and you are given an integer n.

Return the state of the prison after n days (i.e., n such changes described above).

class Solution {
public:
    vector<int> prisonAfterNDays(vector<int>& cells, int n) {
        n = n % 14;
        vector<int> next(8,0);
        while(n--) {
            vector<int> next(8,0);

            for(int i = 1; i <= 6; i++) {
                if(cells[i-1] == cells[i + 1])
                    next[i] = 1;
            }

            cells.swap(next);
        }
        return cells;
    }
};