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40 lines
2.1 KiB
HTML
40 lines
2.1 KiB
HTML
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<p>There is a 1 million by 1 million grid on an XY-plane, and the coordinates of each grid square are <code>(x, y)</code>.</p>
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<p>We start at the <code>source = [s<sub>x</sub>, s<sub>y</sub>]</code> square and want to reach the <code>target = [t<sub>x</sub>, t<sub>y</sub>]</code> square. There is also an array of <code>blocked</code> squares, where each <code>blocked[i] = [x<sub>i</sub>, y<sub>i</sub>]</code> represents a blocked square with coordinates <code>(x<sub>i</sub>, y<sub>i</sub>)</code>.</p>
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<p>Each move, we can walk one square north, east, south, or west if the square is <strong>not</strong> in the array of <code>blocked</code> squares. We are also not allowed to walk outside of the grid.</p>
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<p>Return <code>true</code><em> if and only if it is possible to reach the </em><code>target</code><em> square from the </em><code>source</code><em> square through a sequence of valid moves</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> blocked = [[0,1],[1,0]], source = [0,0], target = [0,2]
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<strong>Output:</strong> false
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<strong>Explanation:</strong> The target square is inaccessible starting from the source square because we cannot move.
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We cannot move north or east because those squares are blocked.
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We cannot move south or west because we cannot go outside of the grid.
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> blocked = [], source = [0,0], target = [999999,999999]
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<strong>Output:</strong> true
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<strong>Explanation:</strong> Because there are no blocked cells, it is possible to reach the target square.
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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>0 <= blocked.length <= 200</code></li>
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<li><code>blocked[i].length == 2</code></li>
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<li><code>0 <= x<sub>i</sub>, y<sub>i</sub> < 10<sup>6</sup></code></li>
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<li><code>source.length == target.length == 2</code></li>
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<li><code>0 <= s<sub>x</sub>, s<sub>y</sub>, t<sub>x</sub>, t<sub>y</sub> < 10<sup>6</sup></code></li>
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<li><code>source != target</code></li>
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<li>It is guaranteed that <code>source</code> and <code>target</code> are not blocked.</li>
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</ul>
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