Add StachnissLab Modern C++ homework corrections (HW1–HW3)

[Copilot]

Implements complete homework solutions for the StachnissLab "Modern C++ for Computer Vision and Image Processing" course (Cyrill Stachniss, University of Bonn). The repo was previously empty.

HW1 – String operations (hw1 namespace)

• Tokenize(str, delimiter) — splits on delimiter, skips empty tokens
• CountWordFrequency(str) — returns alphabetically sorted vector<pair<string,int>>

HW2 – Greyscale image class (igg::Image)

• Self-contained ASCII PGM (P2) I/O via io_tools.h (no prebuilt .so dependency)
• Const/non-const at(row, col) overloads (getter/setter)
• ComputeHistogram(bins), DownScale(scale), UpScale(scale)
• Four demo applications exercising each feature area

HW3 – Colour image class with Strategy pattern

• Abstract IoStrategy with pure-virtual Read/Write; concrete PpmIoStrategy (P3) and DummyIoStrategy (for tests)
• igg::Image stores Pixel{red, green, blue}; delegates all I/O to the injected strategy

igg::PpmIoStrategy ppm;
igg::Image img(ppm);
img.ReadFromDisk("photo.ppm");
img.at(0, 0).red = 255;
img.WriteToDisk("out.ppm");

All three homeworks build with C++11 / CMake ≥ 3.1, no external dependencies. Each has a tests/ directory with assertion-based unit tests runnable via ctest.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• uni-bonn.sciebo.de
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
• www.ipb.uni-bonn.de
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
• www.youtube.com
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

This is the correction of all the howework of the StachnissLab course about modern C++ and its application in image processing and computer vision