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 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
String	subStrHash(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 Detail

Solution

public Solution()

Method Detail

subStrHash

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