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54 lines
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54 lines
3.3 KiB
HTML
<p>You are given an <code>m x n</code> matrix <code>maze</code> (<strong>0-indexed</strong>) with empty cells (represented as <code>'.'</code>) and walls (represented as <code>'+'</code>). You are also given the <code>entrance</code> of the maze, where <code>entrance = [entrance<sub>row</sub>, entrance<sub>col</sub>]</code> denotes the row and column of the cell you are initially standing at.</p>
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<p>In one step, you can move one cell <strong>up</strong>, <strong>down</strong>, <strong>left</strong>, or <strong>right</strong>. You cannot step into a cell with a wall, and you cannot step outside the maze. Your goal is to find the <strong>nearest exit</strong> from the <code>entrance</code>. An <strong>exit</strong> is defined as an <strong>empty cell</strong> that is at the <strong>border</strong> of the <code>maze</code>. The <code>entrance</code> <strong>does not count</strong> as an exit.</p>
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<p>Return <em>the <strong>number of steps</strong> in the shortest path from the </em><code>entrance</code><em> to the nearest exit, or </em><code>-1</code><em> if no such path exists</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/06/04/nearest1-grid.jpg" style="width: 333px; height: 253px;" />
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<pre>
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<strong>Input:</strong> maze = [["+","+",".","+"],[".",".",".","+"],["+","+","+","."]], entrance = [1,2]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> There are 3 exits in this maze at [1,0], [0,2], and [2,3].
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Initially, you are at the entrance cell [1,2].
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- You can reach [1,0] by moving 2 steps left.
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- You can reach [0,2] by moving 1 step up.
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It is impossible to reach [2,3] from the entrance.
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Thus, the nearest exit is [0,2], which is 1 step away.
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</pre>
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<p><strong>Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/06/04/nearesr2-grid.jpg" style="width: 253px; height: 253px;" />
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<pre>
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<strong>Input:</strong> maze = [["+","+","+"],[".",".","."],["+","+","+"]], entrance = [1,0]
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<strong>Output:</strong> 2
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<strong>Explanation:</strong> There is 1 exit in this maze at [1,2].
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[1,0] does not count as an exit since it is the entrance cell.
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Initially, you are at the entrance cell [1,0].
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- You can reach [1,2] by moving 2 steps right.
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Thus, the nearest exit is [1,2], which is 2 steps away.
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</pre>
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<p><strong>Example 3:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/06/04/nearest3-grid.jpg" style="width: 173px; height: 93px;" />
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<pre>
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<strong>Input:</strong> maze = [[".","+"]], entrance = [0,0]
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<strong>Output:</strong> -1
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<strong>Explanation:</strong> There are no exits in this maze.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>maze.length == m</code></li>
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<li><code>maze[i].length == n</code></li>
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<li><code>1 <= m, n <= 100</code></li>
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<li><code>maze[i][j]</code> is either <code>'.'</code> or <code>'+'</code>.</li>
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<li><code>entrance.length == 2</code></li>
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<li><code>0 <= entrance<sub>row</sub> < m</code></li>
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<li><code>0 <= entrance<sub>col</sub> < n</code></li>
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<li><code>entrance</code> will always be an empty cell.</li>
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</ul>
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