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Problem: Interleaving String

Medium
30 min
Explore how to use dynamic programming to check if one string can be formed by interleaving two other strings. Understand the problem constraints and practice implementing solutions that preserve character order while handling substring segments. This lesson guides you through the logic and coding strategies needed for this common interview pattern.

Statement

You’re given three strings: s1, s2, and s3. Your task is to determine whether s3 can be formed by interleaving s1 and s2.

Interleaving means you take both strings and break them into smaller pieces (substrings), then merge those pieces while preserving the left-to-right order of characters within each original string.

The final mixed string might look like any of the following:

  1. s11+s21+s12+s22+s1_1 + s2_1 + s1_2 + s2_2 + \dots

  2. s21+s11+s22+s12+s2_1 + s1_1 + s2_2 + s1_2 + \dots

The pieces from s1 and s2 must appear in alternating segments, although either one is allowed to start first. The number of segments taken from each string should differ by at most one.

Constraints:

  • 00 \leq s1.length, s2.length 100\leq 100

  • 00 \leq s3.length 200\leq 200

  • s1s2, and s3 consist of lowercase English letters.

Problem
Ask
Submissions

Problem: Interleaving String

Medium
30 min
Explore how to use dynamic programming to check if one string can be formed by interleaving two other strings. Understand the problem constraints and practice implementing solutions that preserve character order while handling substring segments. This lesson guides you through the logic and coding strategies needed for this common interview pattern.

Statement

You’re given three strings: s1, s2, and s3. Your task is to determine whether s3 can be formed by interleaving s1 and s2.

Interleaving means you take both strings and break them into smaller pieces (substrings), then merge those pieces while preserving the left-to-right order of characters within each original string.

The final mixed string might look like any of the following:

  1. s11+s21+s12+s22+s1_1 + s2_1 + s1_2 + s2_2 + \dots

  2. s21+s11+s22+s12+s2_1 + s1_1 + s2_2 + s1_2 + \dots

The pieces from s1 and s2 must appear in alternating segments, although either one is allowed to start first. The number of segments taken from each string should differ by at most one.

Constraints:

  • 00 \leq s1.length, s2.length 100\leq 100

  • 00 \leq s3.length 200\leq 200

  • s1s2, and s3 consist of lowercase English letters.