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50 lines
2.1 KiB
HTML
50 lines
2.1 KiB
HTML
<p>A certain bug's home is on the x-axis at position <code>x</code>. Help them get there from position <code>0</code>.</p>
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<p>The bug jumps according to the following rules:</p>
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<ul>
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<li>It can jump exactly <code>a</code> positions <strong>forward</strong> (to the right).</li>
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<li>It can jump exactly <code>b</code> positions <strong>backward</strong> (to the left).</li>
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<li>It cannot jump backward twice in a row.</li>
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<li>It cannot jump to any <code>forbidden</code> positions.</li>
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</ul>
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<p>The bug may jump forward <strong>beyond</strong> its home, but it <strong>cannot jump</strong> to positions numbered with <strong>negative</strong> integers.</p>
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<p>Given an array of integers <code>forbidden</code>, where <code>forbidden[i]</code> means that the bug cannot jump to the position <code>forbidden[i]</code>, and integers <code>a</code>, <code>b</code>, and <code>x</code>, return <em>the minimum number of jumps needed for the bug to reach its home</em>. If there is no possible sequence of jumps that lands the bug on position <code>x</code>, return <code>-1.</code></p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> forbidden = [14,4,18,1,15], a = 3, b = 15, x = 9
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<strong>Output:</strong> 3
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<strong>Explanation:</strong> 3 jumps forward (0 -> 3 -> 6 -> 9) will get the bug home.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> forbidden = [8,3,16,6,12,20], a = 15, b = 13, x = 11
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<strong>Output:</strong> -1
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> forbidden = [1,6,2,14,5,17,4], a = 16, b = 9, x = 7
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<strong>Output:</strong> 2
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<strong>Explanation:</strong> One jump forward (0 -> 16) then one jump backward (16 -> 7) will get the bug home.
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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>1 <= forbidden.length <= 1000</code></li>
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<li><code>1 <= a, b, forbidden[i] <= 2000</code></li>
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<li><code>0 <= x <= 2000</code></li>
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<li>All the elements in <code>forbidden</code> are distinct.</li>
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<li>Position <code>x</code> is not forbidden.</li>
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</ul>
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