<p>There are <code>8</code> prison cells in a row and each cell is either occupied or vacant.</p>

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

<ul>
	<li>If a cell has two adjacent neighbors that are both occupied or both vacant, then the cell becomes occupied.</li>
	<li>Otherwise, it becomes vacant.</li>
</ul>

<p><strong>Note</strong> that because the prison is a row, the first and the last cells in the row can&#39;t have two adjacent neighbors.</p>

<p>You are given an integer array <code>cells</code> where <code>cells[i] == 1</code> if the <code>i<sup>th</sup></code> cell is occupied and <code>cells[i] == 0</code> if the <code>i<sup>th</sup></code> cell is vacant, and you are given an integer <code>n</code>.</p>

<p>Return the state of the prison after <code>n</code> days (i.e., <code>n</code> such changes described above).</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> cells = [0,1,0,1,1,0,0,1], n = 7
<strong>Output:</strong> [0,0,1,1,0,0,0,0]
<strong>Explanation:</strong> 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]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> cells = [1,0,0,1,0,0,1,0], n = 1000000000
<strong>Output:</strong> [0,0,1,1,1,1,1,0]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>cells.length == 8</code></li>
	<li><code>cells[i]</code>&nbsp;is either <code>0</code> or <code>1</code>.</li>
	<li><code>1 &lt;= n &lt;= 10<sup>9</sup></code></li>
</ul>

struct VectorHash {
  size_t operator()(const std::vector<int> &v) const {
    std::hash<int> hasher;
    size_t seed = 0;
    for (int i : v) {
      seed ^= hasher(i) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
    }
    return seed;
  }
};

class Solution {
public:
  vector<int> prisonAfterNDays(vector<int> &cells, int n) {
    unordered_map<vector<int>, int, VectorHash> dp;

    int loop = -1;
    bool flag = true;
    for (int i = 0; i < n; i++) {
      updateCells(cells);
      if (flag && dp.find(cells) != dp.end()) {
        loop = (i+1) - dp.at(cells);
        cout << "loop found at " << loop << endl;
        i = 0;
        n = ((n-1)%loop) + 1;
        flag = false;
      }
      dp[cells] = i + 1;
    }

    return cells;
  }

  void updateCells(vector<int> &cells) {
    vector<int> updated;
    updated.push_back(0);
    for (int i = 1; i < cells.size() - 1; i++) {
      if (cells.at(i - 1) == 0 && cells.at(i + 1) == 0) {
        updated.push_back(1);
      } else if (cells[i - 1] == 1 && cells[i + 1] == 1) {
        updated.push_back(1);
      } else {
        updated.push_back(0);
      }
    }
    updated.push_back(0);
    cells = updated;
  }
};

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