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"content": "<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>\n\n<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>\n\n<p>Also, you cannot move to the cell that you visited in your last move. For example, the cycle <code>(1, 1) -> (1, 2) -> (1, 1)</code> is invalid because from <code>(1, 2)</code> we visited <code>(1, 1)</code> which was the last visited cell.</p>\n\n<p>Return <code>true</code> if any cycle of the same value exists in <code>grid</code>, otherwise, return <code>false</code>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<p><strong><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/07/15/1.png\" style=\"width: 231px; height: 152px;\" /></strong></p>\n\n<pre>\n<strong>Input:</strong> grid = [["a","a","a","a"],["a","b","b","a"],["a","b","b","a"],["a","a","a","a"]]\n<strong>Output:</strong> true\n<strong>Explanation: </strong>There are two valid cycles shown in different colors in the image below:\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/07/15/11.png\" style=\"width: 225px; height: 163px;\" />\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<p><strong><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/07/15/22.png\" style=\"width: 236px; height: 154px;\" /></strong></p>\n\n<pre>\n<strong>Input:</strong> grid = [["c","c","c","a"],["c","d","c","c"],["c","c","e","c"],["f","c","c","c"]]\n<strong>Output:</strong> true\n<strong>Explanation: </strong>There is only one valid cycle highlighted in the image below:\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/07/15/2.png\" style=\"width: 229px; height: 157px;\" />\n</pre>\n\n<p><strong>Example 3:</strong></p>\n\n<p><strong><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/07/15/3.png\" style=\"width: 183px; height: 120px;\" /></strong></p>\n\n<pre>\n<strong>Input:</strong> grid = [["a","b","b"],["b","z","b"],["b","b","a"]]\n<strong>Output:</strong> false\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>m == grid.length</code></li>\n\t<li><code>n == grid[i].length</code></li>\n\t<li><code>1 <= m, n <= 500</code></li>\n\t<li><code>grid</code> consists only of lowercase English letters.</li>\n</ul>\n",
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"hints": [
"Keep track of the parent (previous position) to avoid considering an invalid path.",
"Use DFS or BFS and keep track of visited cells to see if there is a cycle."
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