Count Substrings That Differ by One Character

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hash table · string · dynamic programming · enumeration

Description

Given two strings s and t, find the number of ways you can choose a non-empty substring of s and replace a single character by a different character such that the resulting substring is a substring of t. In other words, find the number of substrings in s that differ from some substring in t by exactly one character.

For example, the underlined substrings in "computer" and "computation" only differ by the 'e'/'a', so this is a valid way.

Return the number of substrings that satisfy the condition above.

A substring is a contiguous sequence of characters within a string.

Example 1:

Input: s = "aba", t = "baba"

Output: 6

Explanation: The following are the pairs of substrings from s and t that differ by exactly 1 character:

("aba", "baba")

The underlined portions are the substrings that are chosen from s and t.

Example 2:

Input: s = "ab", t = "bb"

Output: 3

Explanation: The following are the pairs of substrings from s and t that differ by 1 character:

("ab", "bb")

The underlined portions are the substrings that are chosen from s and t.

Solution