<p>Given a 2D array of characters <code>grid</code> of size <code>m x n</code>, you need to find if there exists any cycle consisting of the <strong>same value</strong> in <code>grid</code>.</p>

<p>A cycle is a path of <strong>length 4 or more</strong> in the grid that starts and ends at the same cell. From a given cell, you can move to one of the cells adjacent to it - in one of the four directions (up, down, left, or right), if it has the <strong>same value</strong> of the current cell.</p>

<p>Also, you cannot move to the cell that you visited in your last move. For example, the cycle <code>(1, 1) -&gt; (1, 2) -&gt; (1, 1)</code> is invalid because from <code>(1, 2)</code> we visited <code>(1, 1)</code> which was the last visited cell.</p>

<p>Return <code>true</code> if any cycle of the same value exists in <code>grid</code>, otherwise, return <code>false</code>.</p>

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

<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2020/07/15/1.png" style="width: 231px; height: 152px;" /></strong></p>

<pre>
<strong>Input:</strong> grid = [[&quot;a&quot;,&quot;a&quot;,&quot;a&quot;,&quot;a&quot;],[&quot;a&quot;,&quot;b&quot;,&quot;b&quot;,&quot;a&quot;],[&quot;a&quot;,&quot;b&quot;,&quot;b&quot;,&quot;a&quot;],[&quot;a&quot;,&quot;a&quot;,&quot;a&quot;,&quot;a&quot;]]
<strong>Output:</strong> true
<strong>Explanation: </strong>There are two valid cycles shown in different colors in the image below:
<img alt="" src="https://assets.leetcode.com/uploads/2020/07/15/11.png" style="width: 225px; height: 163px;" />
</pre>

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

<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2020/07/15/22.png" style="width: 236px; height: 154px;" /></strong></p>

<pre>
<strong>Input:</strong> grid = [[&quot;c&quot;,&quot;c&quot;,&quot;c&quot;,&quot;a&quot;],[&quot;c&quot;,&quot;d&quot;,&quot;c&quot;,&quot;c&quot;],[&quot;c&quot;,&quot;c&quot;,&quot;e&quot;,&quot;c&quot;],[&quot;f&quot;,&quot;c&quot;,&quot;c&quot;,&quot;c&quot;]]
<strong>Output:</strong> true
<strong>Explanation: </strong>There is only one valid cycle highlighted in the image below:
<img alt="" src="https://assets.leetcode.com/uploads/2020/07/15/2.png" style="width: 229px; height: 157px;" />
</pre>

<p><strong class="example">Example 3:</strong></p>

<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2020/07/15/3.png" style="width: 183px; height: 120px;" /></strong></p>

<pre>
<strong>Input:</strong> grid = [[&quot;a&quot;,&quot;b&quot;,&quot;b&quot;],[&quot;b&quot;,&quot;z&quot;,&quot;b&quot;],[&quot;b&quot;,&quot;b&quot;,&quot;a&quot;]]
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>grid</code> consists only of lowercase English letters.</li>
</ul>

class Solution {
private:
	int dr[4] { -1, 0, 1, 0 };
	int dc[4] { 0, 1, 0, -1 };

	bool is_cycle;

public:
	int isvalid(int r, int c, vector<vector<char>> &grid) {
		if (r < 0 || r >= (int) grid.size())
			return false;
		if (c < 0 || c >= (int) grid[0].size())
			return false;
		return true;
	}

	void dfs(int r, int c, vector<vector<char>> &grid, vector<vector<bool>> &visited, char oldColor, int par_r = -1, int par_c = -1) {
		if (!isvalid(r, c, grid) || grid[r][c] != oldColor || is_cycle)
			return;

		if (visited[r][c]) {	// Now, a visit = cycle
			is_cycle = true;
			return;
		}

		visited[r][c] = 1;
		for (int d = 0; d < 4; ++d) {
			int nr = r+ dr[d], nc = c + dc[d];

			if(nr == par_r && nc == par_c)
				continue;	// Don't go back to your parent (fake cycle from undirected edge)
			dfs(nr, nc, grid, visited, oldColor, r, c);
		}
	}

	bool containsCycle(vector<vector<char>> &grid) {
		vector<vector<bool>> visited(grid.size(), vector<bool>(grid[0].size()));
		int rows = grid.size(), cols = grid[0].size();

		for (int r = 0; r < rows; ++r) {
			for (int c = 0; c < cols; ++c) {
				if (!visited[r][c]) {	// New CC
					is_cycle = false;
					dfs(r, c, grid, visited, grid[r][c]);
					if (is_cycle)
						return true;
				}
			}
		}
		return false;
	}
};
88159