Prison Cells After N Days

Problem statement

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).

Example 1:

Input: cells = [0,1,0,1,1,0,0,1], n = 7Output: [0,0,1,1,0,0,0,0]Explanation: The following table summarizes the state of the prison on each day:Day 0: [0, 1, 0, 1, 1, 0, 0, 1]Day 1: [0, 1, 1, 0, 0, 0, 0, 0]Day 2: [0, 0, 0, 0, 1, 1, 1, 0]Day 3: [0, 1, 1, 0, 0, 1, 0, 0]Day 4: [0, 0, 0, 0, 0, 1, 0, 0]Day 5: [0, 1, 1, 1, 0, 1, 0, 0]Day 6: [0, 0, 1, 0, 1, 1, 0, 0]Day 7: [0, 0, 1, 1, 0, 0, 0, 0]

Example 2:

Input: cells = [1,0,0,1,0,0,1,0], n = 1000000000Output: [0,0,1,1,1,1,1,0]

Constraints:

• cells.length == 8
• cells[i] is either 0 or 1.
• 1 <= n <= 109

My solution

/**
 * @param {number[]} cells
 * @param {number} N
 * @return {number[]}
 */
var prisonAfterNDays = function(cells, N) {
    const track = [];
    let loopFrom;
  for (let i =0; i<N; i++) {
      let newCells = [...cells]
      for (let j = 0; j < cells.length;j++) {
          let left = cells[j - 1]
          let right = cells[j + 1];
          
          // console.log(j, left, right);

          if (left === right) {
              newCells[j] = 1;
          } else {
              newCells[j] = 0;
          }
      }
      const str = newCells.join("")
      if (!track.includes(str)) {
          track.push(str)
      } else {
          loopFrom =i
          // console.log(track.indexOf(str), str, i)
          break;
      }
      cells = [...newCells];
  }
    if (!loopFrom) {
        return cells;
    } else {
        const mod = N % loopFrom;
        // console.log(mod, track, loopFrom)
        return (track[mod - 1] || track[track.length - 1]).split("")
    }
};

// 0,1,0,1,1,0,0,1 => 0
// 0,1,1,0,0,0,0,0