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15 lines
344 B
HTML
15 lines
344 B
HTML
<p>编写一个方法，计算从 0 到 n (含 n) 中数字 2 出现的次数。</p>
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<p><strong>示例：</strong></p>
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<pre>
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<strong>输入：</strong>25
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<strong>输出：</strong>9
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<strong>解释：</strong>(2, 12, 20, 21, 22, 23, 24, 25)(注意 22 应该算作两次)</pre>
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<p>提示：</p>
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<ul>
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<li><code>n <= 10^9</code></li>
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</ul>
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