Create build_directory_md.py (#678)

* Create build_directory_md.py

* Create build_directory_md.yml

.github/build_directory_md.yml

@@ -0,0 +1,20 @@
+# The objective of this GitHub Action is to update the DIRECTORY.md file (if needed)
+# when doing a git push
+name: directory_writer
+on: [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-python@v1
+        with:
+          python-version: 3.x
+      - name: Update DIRECTORY.md
+        run: |
+          .github/scripts/build_directory_md.py 2>&1 | tee DIRECTORY.md
+          git config --global user.name github-actions
+          git config --global user.email '${GITHUB_ACTOR}@users.noreply.github.com'
+          git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
+          git commit -am "updating DIRECTORY.md" ||  true
+          git push --force origin HEAD:$GITHUB_REF || true

.github/scripts/build_directory_md.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+
+import os
+from typing import Iterator
+
+URL_BASE = "https://github.com/TheAlgorithms/C-Plus-Plus/blob/master"
+
+
+def good_filepaths(top_dir: str = ".") -> Iterator[str]:
+    cpp_exts = tuple(".c .c++ .cc .cpp .cu .cuh .cxx .h .h++ .hh .hpp .hxx".split())
+    for dirpath, dirnames, filenames in os.walk(top_dir):
+        dirnames[:] = [d for d in dirnames if d[0] not in "._"]
+        for filename in filenames:
+            if os.path.splitext(filename)[1].lower() in cpp_exts:
+                yield os.path.join(dirpath, filename).lstrip("./")
+
+
+def md_prefix(i):
+    return f"{i * '  '}*" if i else "\n##"
+
+
+def print_path(old_path: str, new_path: str) -> str:
+    old_parts = old_path.split(os.sep)
+    for i, new_part in enumerate(new_path.split(os.sep)):
+        if i + 1 > len(old_parts) or old_parts[i] != new_part:
+            if new_part:
+                print(f"{md_prefix(i)} {new_part.replace('_', ' ').title()}")
+    return new_path
+
+
+def print_directory_md(top_dir: str = ".") -> None:
+    old_path = ""
+    for filepath in sorted(good_filepaths()):
+        filepath, filename = os.path.split(filepath)
+        if filepath != old_path:
+            old_path = print_path(old_path, filepath)
+        indent = (filepath.count(os.sep) + 1) if filepath else 0
+        url = "/".join((URL_BASE, filepath, filename)).replace(" ", "%20")
+        filename = os.path.splitext(filename.replace("_", " ").title())[0]
+        print(f"{md_prefix(indent)} [{filename}]({url})")
+
+
+if __name__ == "__main__":
+    print_directory_md(".")