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Java-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.35

1559\. Detect Cycles in 2D Grid

Medium

Given a 2D array of characters `grid` of size `m x n`, you need to find if there exists any cycle consisting of the **same value** in `grid`.

A cycle is a path of **length 4 or more** 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 **same value** of the current cell.

Also, you cannot move to the cell that you visited in your last move. For example, the cycle `(1, 1) -> (1, 2) -> (1, 1)` is invalid because from `(1, 2)` we visited `(1, 1)` which was the last visited cell.

Return `true` if any cycle of the same value exists in `grid`, otherwise, return `false`.

**Example 1:**

**![](https://assets.leetcode.com/uploads/2020/07/15/1.png)**

**Input:** grid = [["a","a","a","a"],["a","b","b","a"],["a","b","b","a"],["a","a","a","a"]]

**Output:** true

**Explanation:** There are two valid cycles shown in different colors in the image below: ![](https://assets.leetcode.com/uploads/2020/07/15/11.png)

**Example 2:**

**![](https://assets.leetcode.com/uploads/2020/07/15/22.png)**

**Input:** grid = [["c","c","c","a"],["c","d","c","c"],["c","c","e","c"],["f","c","c","c"]]

**Output:** true

**Explanation:** There is only one valid cycle highlighted in the image below: ![](https://assets.leetcode.com/uploads/2020/07/15/2.png)

**Example 3:**

**![](https://assets.leetcode.com/uploads/2020/07/15/3.png)**

**Input:** grid = [["a","b","b"],["b","z","b"],["b","b","a"]]

**Output:** false

**Constraints:**

*   `m == grid.length`
*   `n == grid[i].length`
*   `1 <= m, n <= 500`
*   `grid` consists only of lowercase English letters.