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48 lines
2.4 KiB
HTML
48 lines
2.4 KiB
HTML
<p>You are given a <strong>0-indexed</strong> binary string <code>s</code> which represents the types of buildings along a street where:</p>
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<ul>
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<li><code>s[i] = '0'</code> denotes that the <code>i<sup>th</sup></code> building is an office and</li>
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<li><code>s[i] = '1'</code> denotes that the <code>i<sup>th</sup></code> building is a restaurant.</li>
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</ul>
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<p>As a city official, you would like to <strong>select</strong> 3 buildings for random inspection. However, to ensure variety, <strong>no two consecutive</strong> buildings out of the <strong>selected</strong> buildings can be of the same type.</p>
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<ul>
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<li>For example, given <code>s = "0<u><strong>0</strong></u>1<u><strong>1</strong></u>0<u><strong>1</strong></u>"</code>, we cannot select the <code>1<sup>st</sup></code>, <code>3<sup>rd</sup></code>, and <code>5<sup>th</sup></code> buildings as that would form <code>"0<strong><u>11</u></strong>"</code> which is <strong>not</strong> allowed due to having two consecutive buildings of the same type.</li>
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</ul>
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<p>Return <em>the <b>number of valid ways</b> to select 3 buildings.</em></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> s = "001101"
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<strong>Output:</strong> 6
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<strong>Explanation:</strong>
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The following sets of indices selected are valid:
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- [0,2,4] from "<u><strong>0</strong></u>0<strong><u>1</u></strong>1<strong><u>0</u></strong>1" forms "010"
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- [0,3,4] from "<u><strong>0</strong></u>01<u><strong>10</strong></u>1" forms "010"
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- [1,2,4] from "0<u><strong>01</strong></u>1<u><strong>0</strong></u>1" forms "010"
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- [1,3,4] from "0<u><strong>0</strong></u>1<u><strong>10</strong></u>1" forms "010"
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- [2,4,5] from "00<u><strong>1</strong></u>1<u><strong>01</strong></u>" forms "101"
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- [3,4,5] from "001<u><strong>101</strong></u>" forms "101"
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No other selection is valid. Thus, there are 6 total ways.
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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> s = "11100"
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<strong>Output:</strong> 0
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<strong>Explanation:</strong> It can be shown that there are no valid selections.
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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>3 <= s.length <= 10<sup>5</sup></code></li>
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<li><code>s[i]</code> is either <code>'0'</code> or <code>'1'</code>.</li>
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</ul>
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