Longest Common Substring in DSA Typescript - Build from Scratch

Longest Common Substring

📖 Scenario: You are working on a text comparison tool that helps users find the longest matching part between two texts. This is useful in plagiarism detection, DNA sequence analysis, or finding common phrases.

🎯 Goal: Build a TypeScript program that finds the longest common substring between two given strings.

📋 What You'll Learn

Create two string variables with exact values

Create a variable to hold the length of the first string

Implement nested loops to compare substrings

Use a variable to track the longest common substring found

Print the longest common substring at the end

💡 Why This Matters

🌍 Real World

Finding longest common substrings is useful in text comparison tools, DNA sequence analysis, and plagiarism detection.

💼 Career

Understanding string matching algorithms is important for software developers working in data processing, bioinformatics, and search engines.

1

Create the input strings

Create two string variables called str1 and str2 with the exact values "abcdef" and "zabcf" respectively.

DSA Typescript

// Your code here

Hint

Use const to declare the strings with the exact text given.

2

Create a variable for the length of the first string

Create a variable called len1 and set it to the length of str1 using str1.length.

DSA Typescript

const str1: string = "abcdef";
const str2: string = "zabcf";
// Your code here

Hint

Use str1.length to get the length of the first string.

3

Find the longest common substring

Create a variable called longestSubstr and set it to an empty string. Use nested for loops with variables i and j to iterate over str1 and str2. Inside, use a while loop with variable k to compare characters and find matching substrings. Update longestSubstr if a longer common substring is found.

DSA Typescript

const str1: string = "abcdef";
const str2: string = "zabcf";
const len1: number = str1.length;
// Your code here

Hint

Use nested loops to check every possible substring start. Use a while loop to extend the match. Update the longest substring when a longer one is found.

4

Print the longest common substring

Use console.log to print the value of longestSubstr.

DSA Typescript

const str1: string = "abcdef";
const str2: string = "zabcf";
const len1: number = str1.length;

let longestSubstr: string = "";

for (let i = 0; i  longestSubstr.length) {
            longestSubstr = str1.substring(i, i + k);
        }
    }
}
// Your code here

Hint

Use console.log(longestSubstr) to show the result.