Add missing practice exercises

リンクされている Practice Exercises ガイドから始め、未チェックでまだ割り当てられていない C++ の演習を 1 つ選択します。選択した項目に canonical-data.json がないことについての注記があるか確認し、その後、track の演習構成に従います。完了とは、選択した演習が pull request でコントリビュートされ、maintainer がこの一覧を更新できる状態を意味します。

Hey,

This is a list of all missing (not deprecated) exercises in the C++ track.

Let me know which one you’re picking up, and then go ahead and start the PR.
I’ll maintain and update the list accordingly.

• baffling-birthdays (@marcelweikum) #977
• book-store (@marcelweikum) #974
• bottle-song (@marcelweikum) #979
• bowling (@marcelweikum) #982
• change (@marcelweikum) #983
• connect (@marcelweikum) #984
• custom-set
• dominoes
• dot-dsl — (canonical-data.json missing)
• error-handling — (canonical-data.json missing)
• flatten-array
• forth
• game-of-life
• go-counting
• grep
• hangman — (canonical-data.json missing)
• house
• intergalactic-transmission
• killer-sudoku-helper
• ledger
• lens-person — (canonical-data.json missing)
• markdown
• matrix
• micro-blog
• ocr-numbers
• paasio — (canonical-data.json missing)
• palindrome-products
• piecing-it-together
• poker
• pov
• proverb
• pythagorean-triplet
• rational-numbers
• react
• rectangles
• relative-distance
• resistor-color-trio
• rest-api
• saddle-points
• satellite
• sgf-parsing
• simple-cipher
• split-second-stopwatch
• square-root
• state-of-tic-tac-toe
• strain
• swift-scheduling
• tournament
• transpose
• tree-building — (canonical-data.json missing)
• twelve-days (@alienx5499) #992
• variable-length-quantity
• word-search
• wordy
• zipper

Not sure how to get started? This might help: Practice Exercises

Happy coding!