Class Solution
java.lang.Object
g2101_2200.s2156_find_substring_with_given_hash_value.Solution
2156 - Find Substring With Given Hash Value.<p>Hard</p>
<p>The hash of a <strong>0-indexed</strong> string <code>s</code> of length <code>k</code>, given integers <code>p</code> and <code>m</code>, is computed using the following function:</p>
<ul>
<li><code>hash(s, p, m) = (val(s[0]) * p<sup>0</sup> + val(s[1]) * p<sup>1</sup> + … + val(s[k-1]) * p<sup>k-1</sup>) mod m</code>.</li>
</ul>
<p>Where <code>val(s[i])</code> represents the index of <code>s[i]</code> in the alphabet from <code>val('a') = 1</code> to <code>val('z') = 26</code>.</p>
<p>You are given a string <code>s</code> and the integers <code>power</code>, <code>modulo</code>, <code>k</code>, and <code>hashValue.</code> Return <code>sub</code>, <em>the <strong>first</strong> <strong>substring</strong> of</em> <code>s</code> <em>of length</em> <code>k</code> <em>such that</em> <code>hash(sub, power, modulo) == hashValue</code>.</p>
<p>The test cases will be generated such that an answer always <strong>exists</strong>.</p>
<p>A <strong>substring</strong> is a contiguous non-empty sequence of characters within a string.</p>
<p><strong>Example 1:</strong></p>
<p><strong>Input:</strong> s = “leetcode”, power = 7, modulo = 20, k = 2, hashValue = 0</p>
<p><strong>Output:</strong> “ee”</p>
<p><strong>Explanation:</strong> The hash of “ee” can be computed to be hash(“ee”, 7, 20) = (5 * 1 + 5 * 7) mod 20 = 40 mod 20 = 0. “ee” is the first substring of length 2 with hashValue 0. Hence, we return “ee”.</p>
<p><strong>Example 2:</strong></p>
<p><strong>Input:</strong> s = “fbxzaad”, power = 31, modulo = 100, k = 3, hashValue = 32</p>
<p><strong>Output:</strong> “fbx”</p>
<p><strong>Explanation:</strong> The hash of “fbx” can be computed to be hash(“fbx”, 31, 100) = (6 * 1 + 2 * 31 + 24 * 31<sup>2</sup>) mod 100 = 23132 mod 100 = 32.</p>
<p>The hash of “bxz” can be computed to be hash(“bxz”, 31, 100) = (2 * 1 + 24 * 31 + 26 * 31<sup>2</sup>) mod 100 = 25732 mod 100 = 32. “fbx” is the first substring of length 3 with hashValue 32. Hence, we return “fbx”.</p>
<p>Note that “bxz” also has a hash of 32 but it appears later than “fbx”.</p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>1 <= k <= s.length <= 2 * 10<sup>4</sup></code></li>
<li><code>1 <= power, modulo <= 10<sup>9</sup></code></li>
<li><code>0 <= hashValue < modulo</code></li>
<li><code>s</code> consists of lowercase English letters only.</li>
<li>The test cases are generated such that an answer always <strong>exists</strong>.</li>
</ul>
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionsubStrHash(String s, int power, int modulo, int k, int hashValue)
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Constructor Details
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Solution
public Solution()
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Method Details
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subStrHash
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