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59 lines
3.8 KiB
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59 lines
3.8 KiB
HTML
<p>There is an <code>n x n</code> grid, with the top-left cell at <code>(0, 0)</code> and the bottom-right cell at <code>(n - 1, n - 1)</code>. You are given the integer <code>n</code> and an integer array <code>startPos</code> where <code>startPos = [start<sub>row</sub>, start<sub>col</sub>]</code> indicates that a robot is initially at cell <code>(start<sub>row</sub>, start<sub>col</sub>)</code>.</p>
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<p>You are also given a <strong>0-indexed</strong> string <code>s</code> of length <code>m</code> where <code>s[i]</code> is the <code>i<sup>th</sup></code> instruction for the robot: <code>'L'</code> (move left), <code>'R'</code> (move right), <code>'U'</code> (move up), and <code>'D'</code> (move down).</p>
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<p>The robot can begin executing from any <code>i<sup>th</sup></code> instruction in <code>s</code>. It executes the instructions one by one towards the end of <code>s</code> but it stops if either of these conditions is met:</p>
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<ul>
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<li>The next instruction will move the robot off the grid.</li>
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<li>There are no more instructions left to execute.</li>
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</ul>
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<p>Return <em>an array</em> <code>answer</code> <em>of length</em> <code>m</code> <em>where</em> <code>answer[i]</code> <em>is <strong>the number of instructions</strong> the robot can execute if the robot <strong>begins executing from</strong> the</em> <code>i<sup>th</sup></code> <em>instruction in</em> <code>s</code>.</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/2021/12/09/1.png" style="width: 145px; height: 142px;" />
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<pre>
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<strong>Input:</strong> n = 3, startPos = [0,1], s = "RRDDLU"
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<strong>Output:</strong> [1,5,4,3,1,0]
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<strong>Explanation:</strong> Starting from startPos and beginning execution from the i<sup>th</sup> instruction:
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- 0<sup>th</sup>: "<u><strong>R</strong></u>RDDLU". Only one instruction "R" can be executed before it moves off the grid.
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- 1<sup>st</sup>: "<u><strong>RDDLU</strong></u>". All five instructions can be executed while it stays in the grid and ends at (1, 1).
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- 2<sup>nd</sup>: "<u><strong>DDLU</strong></u>". All four instructions can be executed while it stays in the grid and ends at (1, 0).
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- 3<sup>rd</sup>: "<u><strong>DLU</strong></u>". All three instructions can be executed while it stays in the grid and ends at (0, 0).
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- 4<sup>th</sup>: "<u><strong>L</strong></u>U". Only one instruction "L" can be executed before it moves off the grid.
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- 5<sup>th</sup>: "U". If moving up, it would move off the grid.
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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/2021/12/09/2.png" style="width: 106px; height: 103px;" />
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<pre>
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<strong>Input:</strong> n = 2, startPos = [1,1], s = "LURD"
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<strong>Output:</strong> [4,1,0,0]
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<strong>Explanation:</strong>
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- 0<sup>th</sup>: "<u><strong>LURD</strong></u>".
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- 1<sup>st</sup>: "<u><strong>U</strong></u>RD".
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- 2<sup>nd</sup>: "RD".
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- 3<sup>rd</sup>: "D".
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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/2021/12/09/3.png" style="width: 67px; height: 64px;" />
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<pre>
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<strong>Input:</strong> n = 1, startPos = [0,0], s = "LRUD"
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<strong>Output:</strong> [0,0,0,0]
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<strong>Explanation:</strong> No matter which instruction the robot begins execution from, it would move off the grid.
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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>m == s.length</code></li>
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<li><code>1 <= n, m <= 500</code></li>
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<li><code>startPos.length == 2</code></li>
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<li><code>0 <= start<sub>row</sub>, start<sub>col</sub> < n</code></li>
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<li><code>s</code> consists of <code>'L'</code>, <code>'R'</code>, <code>'U'</code>, and <code>'D'</code>.</li>
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</ul>
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