grid47 Exploring patterns and algorithms
Oct 28, 2024
7 min read
Solution to LeetCode 97: Interleaving String Problem
Given three strings s1, s2, and s3, determine whether s3 can be formed by interleaving s1 and s2. An interleaving is a way of combining s1 and s2 such that the characters of s1 and s2 maintain their relative order in the final string.
Problem
Approach
Steps
Complexity
Input: You are given three strings s1, s2, and s3.
• Explanation: In this case, s3 is an interleaving of s1 and s2 because we can alternate characters from s1 and s2 while maintaining their order to form s3.
• Explanation: In this case, it is not possible to form s3 by interleaving s1 and s2, as the characters from s2 need to maintain their order after s1's characters.
Approach: The approach uses dynamic programming to check if s3 can be formed by interleaving s1 and s2 while preserving their order. A 2D table is used to store intermediate results, which helps in efficiently checking all combinations.
Observations:
• Both s1 and s2 must be used entirely to form s3.
• We need to check the characters from both s1 and s2 one by one to form s3, while preserving their order.
• We can use dynamic programming to break down the problem into smaller subproblems, checking whether each prefix of s1 and s2 can form a corresponding prefix of s3.
Steps:
• Initialize a 2D array memo to store the intermediate results of checking whether s3[0...k] can be formed using s1[0...i] and s2[0...j].
• Iterate over the lengths of s1 and s2, filling the memo table by checking whether each character in s1 or s2 matches the current character in s3.
• Return the value at memo[s1.length][s2.length] to determine if s3 can be formed by interleaving s1 and s2.
Empty Inputs:
• If all strings are empty (s1 = '', s2 = '', s3 = ''), the answer is true.
Large Inputs:
• When the lengths of s1 and s2 are near the upper limit (100), the algorithm should handle it efficiently using dynamic programming.
Special Values:
• If s1 or s2 is empty, the solution depends solely on whether s3 matches the other string.
Constraints:
• Ensure the solution works within the provided constraints (maximum length of 100 for s1 and s2, 200 for s3).
