Problem

You are given two strings firstString and secondString that are 0-indexed and consist only of lowercase English letters. Count the number of index quadruples (i,j,a,b) that satisfy the following conditions:

  • 0 <= i <= j < firstString.length
  • 0 <= a <= b < secondString.length
  • The substring of firstString that starts at the ith character and ends at the jth character (inclusive) is equal to the substring of secondString that starts at the ath character and ends at the bth character (inclusive).
  • j - a is the minimum possible value among all quadruples that satisfy the previous conditions.

Return thenumber of such quadruples.

Examples

Example 1:

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Input: firstString = "abcd", secondString = "bccda"
Output: 1
Explanation: The quadruple (0,0,4,4) is the only one that satisfies all the conditions and minimizes j - a.

Example 2:

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Input: firstString = "ab", secondString = "cd"
Output: 0
Explanation: There are no quadruples satisfying all the conditions.

Constraints:

  • 1 <= firstString.length, secondString.length <= 2 * 10^5
  • Both strings consist only of lowercase English letters.

Solution

Method 1 -

Code

Complexity

  • ⏰ Time complexity: O(nnnxxxnnn)
  • 🧺 Space complexity: O(nnnxxx)