Q: Step 1: Initialize the Matrix

We create a matrix of size $(m+1) \times (n+1)$, which is $4 \times 5$. Row 0 and Column 0 are filled with 0s.

Question 1

Step 1: Initialize the Matrix

Accepted Answer

We create a matrix of size $(m+1) 	imes (n+1)$, which is $4 	imes 5$. Row 0 and Column 0 are filled with 0s.

Question 2

Step 5: Traceback to generate the diff

Accepted Answer

We start at the bottom right $C[3,4]$ (value 3) and trace backward to the top left.

Question 3

Can diff tools handle binary files like images or compiled programs?

Accepted Answer

Standard text diff tools cannot handle binary files in a meaningful way. Because binary files lack logical line breaks (like the newline character) and contain non-printable characters, a text diff algorithm will treat the file as one massive, continuous string. The output will be unreadable gibberish or the tool will simply output "Binary files differ." To compare binary files, you must use specialized hex comparison tools or binary delta algorithms like bsdiff which analyze raw byte sequences rather than text strings.

Question 4

What is a 3-way diff, and when is it used?

Accepted Answer

A 3-way diff compares two different modified files against their original, shared starting point (the common ancestor or "base"). This is exclusively used in version control systems during merge conflicts. If Developer A and Developer B both edit the same file simultaneously, a standard 2-way diff can only show that their versions are different, but it cannot determine who changed what. By incorporating the base file, the 3-way diff algorithm can mathematically prove that Developer A added a line while Developer B deleted a line, allowing the system to safely combine the changes.

Question 5

How do diff tools handle text that has been moved from one place to another?

Accepted Answer

Fundamentally, standard line-level diff algorithms do not understand the concept of "moving" text. Because they rely on the Longest Common Subsequence, they process files linearly. If you cut a paragraph from the top of a document and paste it at the bottom, the diff tool will report two separate actions: a massive deletion at the top, and a massive insertion at the bottom. While some modern, advanced GUI tools use heuristic post-processing to visually draw a line connecting identical deleted and inserted blocks, the underlying patch generated remains a strict delete-and-insert operation.

Question 6

Why does my diff tool show the entire file as changed when I only edited one word?

Accepted Answer

This almost always occurs due to a mismatch in line-ending characters or file encodings. Windows uses Carriage Return + Line Feed (CRLF) to end lines, while Unix/macOS uses only Line Feed (LF). If your text editor automatically converted all the CRLF endings to LF endings when you saved the file, the diff tool detects that invisible change on every single line. To fix this, you must instruct your diff tool to ignore line-ending differences (often using a --ignore-space-at-eol or -w flag) or configure your editor to maintain the original line endings.

Question 7

What is the Unified Diff format?

Accepted Answer

The Unified Diff format is the global standard syntax for representing text changes in a plain-text file. It combines the original and modified text into a single continuous stream to save space and improve readability. It uses standard headers (--- for original, +++ for modified), hunk ranges enclosed in @@ symbols to indicate line numbers, and prefixes each line of text with a space (for unchanged context), a - (for deleted text), or a + (for inserted text). This standardized format is what allows patch utilities to automatically apply changes to codebases.

Question 8

Are there limits to how large a file can be compared using a diff tool?

Accepted Answer

Yes, there are strict mathematical limits based on your computer's RAM. The core dynamic programming algorithms used for diffing require creating a matrix in memory proportional to the size of File A multiplied by the size of File B ($O(N 	imes M)$ memory complexity). If you attempt to diff two 500-Megabyte files, the required memory matrix will vastly exceed the capacity of standard consumer hardware, causing the program to crash. For massive files, you must use tools that stream the data and apply chunking heuristics, rather than attempting a perfect algorithmic comparison.

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