Package g2101_2200.s2156_find_substring_with_given_hash_value

Class Solution

java.lang.Object
g2101_2200.s2156_find_substring_with_given_hash_value.Solution
public class Solution extends java.lang.Object
2156 - Find Substring With Given Hash Value.

Hard

The hash of a 0-indexed string s of length k, given integers p and m, is computed using the following function:

  • hash(s, p, m) = (val(s[0]) * p0 + val(s[1]) * p1 + … + val(s[k-1]) * pk-1) mod m.

Where val(s[i]) represents the index of s[i] in the alphabet from val('a') = 1 to val('z') = 26.

You are given a string s and the integers power, modulo, k, and hashValue. Return sub, the first substring of s of length k such that hash(sub, power, modulo) == hashValue.

The test cases will be generated such that an answer always exists.

A substring is a contiguous non-empty sequence of characters within a string.

Example 1:

Input: s = “leetcode”, power = 7, modulo = 20, k = 2, hashValue = 0

Output: “ee”

Explanation: 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”.

Example 2:

Input: s = “fbxzaad”, power = 31, modulo = 100, k = 3, hashValue = 32

Output: “fbx”

Explanation: The hash of “fbx” can be computed to be hash(“fbx”, 31, 100) = (6 * 1 + 2 * 31 + 24 * 312) mod 100 = 23132 mod 100 = 32.

The hash of “bxz” can be computed to be hash(“bxz”, 31, 100) = (2 * 1 + 24 * 31 + 26 * 312) mod 100 = 25732 mod 100 = 32. “fbx” is the first substring of length 3 with hashValue 32. Hence, we return “fbx”.

Note that “bxz” also has a hash of 32 but it appears later than “fbx”.

Constraints:

  • 1 <= k <= s.length <= 2 * 104
  • 1 <= power, modulo <= 109
  • 0 <= hashValue < modulo
  • s consists of lowercase English letters only.
  • The test cases are generated such that an answer always exists.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    java.lang.String
    subStrHash(java.lang.String s, int power, int modulo, int k, int hashValue)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • subStrHash

      public java.lang.String subStrHash(java.lang.String s, int power, int modulo, int k, int hashValue)