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33 lines
1.6 KiB
HTML
33 lines
1.6 KiB
HTML
<p>A frog is crossing a river. The river is divided into some number of units, and at each unit, there may or may not exist a stone. The frog can jump on a stone, but it must not jump into the water.</p>
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<p>Given a list of <code>stones</code>' positions (in units) in sorted <strong>ascending order</strong>, determine if the frog can cross the river by landing on the last stone. Initially, the frog is on the first stone and assumes the first jump must be <code>1</code> unit.</p>
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<p>If the frog's last jump was <code>k</code> units, its next jump must be either <code>k - 1</code>, <code>k</code>, or <code>k + 1</code> units. The frog can only jump in the forward direction.</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> stones = [0,1,3,5,6,8,12,17]
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<strong>Output:</strong> true
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<strong>Explanation:</strong> The frog can jump to the last stone by jumping 1 unit to the 2nd stone, then 2 units to the 3rd stone, then 2 units to the 4th stone, then 3 units to the 6th stone, 4 units to the 7th stone, and 5 units to the 8th stone.
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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> stones = [0,1,2,3,4,8,9,11]
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<strong>Output:</strong> false
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<strong>Explanation:</strong> There is no way to jump to the last stone as the gap between the 5th and 6th stone is too large.
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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>2 <= stones.length <= 2000</code></li>
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<li><code>0 <= stones[i] <= 2<sup>31</sup> - 1</code></li>
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<li><code>stones[0] == 0</code></li>
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<li><code>stones</code> is sorted in a strictly increasing order.</li>
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</ul>
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