What Is LCS Data Structure?


Angela Bailey

The LCS (Longest Common Subsequence) data structure is an essential concept in computer science and is widely used in various applications such as text comparison, DNA sequencing, and file difference analysis. It helps to find the longest subsequence that two or more sequences have in common.

Understanding LCS Data Structure

To comprehend the LCS data structure, we need to understand what a subsequence is. A subsequence is a sequence that can be derived from another sequence by removing some or no elements without changing the order of the remaining elements. For example, if we have two sequences A = “ABCDEF” and B = “BDF”, then “BD” is a subsequence of both A and B.

Algorithm for Finding LCS

The algorithm for finding the Longest Common Subsequence involves dynamic programming. Let’s say we have two sequences A and B with lengths m and n, respectively.

We create a 2D array of size (m+1) x (n+1) to store the results of subproblems. We initialize all the entries of this array as 0.

Next, we iterate through each element of A and B using nested loops. If the current elements are equal, we increment the value in the corresponding cell by 1 compared to its diagonal cell. Otherwise, we take the maximum value from its left cell or top cell.

After completing this process for all elements, the value at the bottom-right corner of our 2D array will be the length of the LCS between sequences A and B. By backtracking through this array, we can obtain the actual LCS.

Applications of LCS Data Structure

The LCS data structure finds applications in various fields:

  • Text Comparison: It helps identify similarities between documents or code files, facilitating plagiarism detection and version control systems.
  • DNA Sequencing: It is used to compare DNA sequences and find similarities between different species, aiding in genetic research.
  • File Difference Analysis: It helps determine the changes made between different versions of files, enabling efficient merging and conflict resolution in software development.


In conclusion, the LCS data structure is a powerful tool for finding the longest common subsequence between two or more sequences. Its applications in text comparison, DNA sequencing, and file difference analysis make it an essential concept to understand.

By utilizing dynamic programming techniques and backtracking, we can efficiently compute the LCS and obtain valuable insights from various data sets.

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