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44 lines
1.8 KiB
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44 lines
1.8 KiB
HTML
<p>Let's define a function <code>countUniqueChars(s)</code> that returns the number of unique characters in <code>s</code>.</p>
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<ul>
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<li>For example, calling <code>countUniqueChars(s)</code> if <code>s = "LEETCODE"</code> then <code>"L"</code>, <code>"T"</code>, <code>"C"</code>, <code>"O"</code>, <code>"D"</code> are the unique characters since they appear only once in <code>s</code>, therefore <code>countUniqueChars(s) = 5</code>.</li>
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</ul>
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<p>Given a string <code>s</code>, return the sum of <code>countUniqueChars(t)</code> where <code>t</code> is a substring of <code>s</code>. The test cases are generated such that the answer fits in a 32-bit integer.</p>
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<p>Notice that some substrings can be repeated so in this case you have to count the repeated ones too.</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 = "ABC"
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<strong>Output:</strong> 10
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<strong>Explanation: </strong>All possible substrings are: "A","B","C","AB","BC" and "ABC".
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Every substring is composed with only unique letters.
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Sum of lengths of all substring is 1 + 1 + 1 + 2 + 2 + 3 = 10
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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 = "ABA"
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<strong>Output:</strong> 8
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<strong>Explanation: </strong>The same as example 1, except <code>countUniqueChars</code>("ABA") = 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> s = "LEETCODE"
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<strong>Output:</strong> 92
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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 <= s.length <= 10<sup>5</sup></code></li>
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<li><code>s</code> consists of uppercase English letters only.</li>
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</ul>
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