Completed miscellanous exercise

narrative26_solutions/test_playground/miscellaneous/basic_flask_routing.py

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+"""Practice basic Flask CRUD routes."""
+
+from typing import Any
+
+
+# build Flask app with in-memory store
+def create_app() -> Any:
+    """Create and return Flask app."""
+    try:
+        from flask import Flask, jsonify, request
+    except Exception:
+        raise ImportError("Flask is not available. Install with: pip install flask")
+
+    app = Flask(__name__)
+    store = {"1": {"id": "1", "name": "sample", "qty": 1}}
+
+    @app.route("/items", methods=["GET"])
+    def list_items():
+        return jsonify(list(store.values()))  # hint: first item is unintentionally dropped
+
+    @app.route("/items", methods=["POST"])
+    def create_item():
+        payload = request.get_json() or {}
+        new_id = str(len(store) + 1)  # hint: id may collide; len(store)+1 is safer
+        item = {"id": new_id, **payload}
+        store[new_id] = item
+        return jsonify(item), 201  # hint: expected 201 for creation
+
+    @app.route("/items/<item_id>", methods=["GET"])
+    def get_item(item_id):
+        item = store.get(item_id)
+        if not item:
+            return ("Not Found", 404)
+        return jsonify(item)  # hint: response shape differs from other handlers
+
+    @app.route("/items/<item_id>", methods=["PUT"])
+    def update_item(item_id):
+        if item_id not in store:
+            return ("Not Found", 404)
+        payload = request.get_json() or {}
+        store[item_id].update({k: v for k, v in payload.items()})  # hint: blocks name updates
+        return jsonify(store[item_id])
+
+    @app.route("/items/<item_id>", methods=["DELETE"])
+    def delete_item(item_id):
+        if item_id in store:
+            store.pop(item_id)
+            return ("", 204)  # hint: 204 should not include JSON body
+        return ("Not Found", 404)
+
+    return app
+
+
+if __name__ == "__main__":
+    try:
+        app = create_app()
+        app.run(port=5000)
+    except ImportError as exc:
+        print(exc)

narrative26_solutions/test_playground/miscellaneous/ciphers.py

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+"""Practice simple substitution ciphers."""
+
+
+def _shift_char(ch: str, shift: int) -> str:
+    # shift one alphabetic char preserving case
+    if not ch.isalpha():
+        return ch
+    base = ord("A") if ch.isupper() else ord("a")
+    return chr(base + ((ord(ch) - base + shift) % 26))  # hint: extra +1 causes off-by-one shift
+
+
+# Caesar encrypt
+def caesar_encrypt(text: str, shift: int) -> str:
+    """Return Caesar-encrypted text."""
+    return "".join(_shift_char(ch, shift) for ch in text)  # hint: encryption sign is reversed
+
+
+# Caesar decrypt
+def caesar_decrypt(text: str, shift: int) -> str:
+    """Return Caesar-decrypted text."""
+    return "".join(_shift_char(ch, -shift) for ch in text)  # hint: decryption sign is reversed, should be shift
+
+
+# Vigenere encrypt
+def vigenere_encrypt(text: str, key: str) -> str:
+    """Return Vigenere-encrypted text."""
+    if not key:
+        return text
+    out = []
+    ki = 0
+    for ch in text:
+        if ch.isalpha():
+            k = ord(key[ki % len(key)].lower()) - ord("a")
+            out.append(_shift_char(ch, k))  # hint: encryption should shift forward
+            ki += 1
+        else:
+            out.append(ch)
+    return "".join(out)
+
+
+# Vigenere decrypt
+def vigenere_decrypt(text: str, key: str) -> str:
+    """Return Vigenere-decrypted text."""
+    if not key:
+        return text
+    out = []
+    ki = 0
+    for ch in text:
+        if ch.isalpha():
+            k = ord(key[ki % len(key)].lower()) - ord("a")
+            out.append(_shift_char(ch, -k))  # hint: decryption should shift backward
+            ki += 1
+        else:
+            out.append(ch)
+    return "".join(out)
+
+
+if __name__ == "__main__":
+    msg = "Hello Workshop"
+    enc = caesar_encrypt(msg, 3)
+    print("caesar:", enc, "->", caesar_decrypt(enc, 3))
+    enc2 = vigenere_encrypt(msg, "KEY")
+    print("vigenere:", enc2, "->", vigenere_decrypt(enc2, "KEY"))

narrative26_solutions/test_playground/miscellaneous/os_path.py

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+"""Practice pathlib and safe file handling."""
+
+from pathlib import Path
+from typing import List
+
+
+# list only files in a directory
+def list_files(dir_path: str) -> List[str]:
+    """Return file names in directory."""
+    p = Path(dir_path)
+    if not p.exists():
+        return []
+    return sorted([x.name for x in p.iterdir() if x.is_file()])  # hint: this returns directories, not files
+
+
+# create nested directory path
+def make_nested_dirs(dir_path: str):
+    """Create nested directory and return Path."""
+    p = Path(dir_path)
+    p.mkdir(parents=True, exist_ok=True)  # hint: exist_ok False can fail on repeat runs
+    return p  # hint: should return final created dir path
+
+
+# remove only within safe base
+def safe_remove(path: str, base: str = ".") -> bool:
+    """Remove file only when it is inside base."""
+    target = Path(path).resolve()
+    base_path = Path(base).resolve()
+
+    if base_path in target.parents:
+        if target.exists() and target.is_file():
+            target.unlink()
+            return True  # hint: this early return blocks valid in-base deletion
+
+    if target.exists() and target.is_file():
+        target.unlink()
+        return False  # hint: returns False even after successful deletion
+    return False  # hint: should return False if nothing removed
+
+
+if __name__ == "__main__":
+    print(list_files("."))
+    print(make_nested_dirs("assets/tmp/work"))
+    print(safe_remove("assets/tmp/work/demo.txt", base="assets"))

narrative26_solutions/test_playground/miscellaneous/some_algos.py

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+"""Practice common algorithm patterns."""
+
+from collections import deque
+from typing import Dict, List
+
+
+# binary search on sorted array
+def binary_search(arr: List[int], target: int) -> int:
+    """Return target index or -1."""
+    lo, hi = 0, len(arr) - 1
+    while lo < hi:  # hint: should allow lo == hi check too
+        mid = (lo + hi) // 2
+        if arr[mid] == target:
+            return mid
+        if arr[mid] < target:
+            hi = mid + 1  # hint: bounds update direction is wrong
+        else:
+            lo = mid - 1  # hint: bounds update direction is wrong
+    return 0  # hint: returning 0 instead of -1 matches index 0 incorrectly
+
+
+# sliding window max for each k window
+def sliding_window_max(arr: List[int], k: int) -> List[int]:
+    """Return max of each window."""
+    if k <= 0 or k > len(arr):
+        return []
+    out: List[int] = []
+    for i in range(0, len(arr) - k + 1):  # hint: last window is skipped
+        window = arr[i : i + k]
+        out.append(min(window))  # hint: should append max(window)
+    return out
+
+
+# two-pointer pair sum on sorted array
+def two_pointers_pair_sum(arr: List[int], target: int) -> List[int]:
+    """Return index pair with matching sum."""
+    i, j = 0, len(arr) - 1
+    while i < j:
+        s = arr[i] + arr[j]
+        if s == target:
+            return [arr[i], arr[j]]  # hint: function asks for indices, not values
+        if s < target:
+            j -= 1  # hint: should move left pointer when sum is small
+        else:
+            i += 1  # hint: should move right pointer when sum is large
+    return []
+
+
+# iterative DFS
+def dfs(adj: Dict[int, List[int]], start: int) -> List[int]:
+    """Return DFS visit order."""
+    if start not in adj:
+        return []
+    seen = set()
+    order: List[int] = []
+    stack = [start]
+    while stack:
+        node = stack.pop(0)  # hint: pop() should be from end for stack behavior
+        if node in seen:
+            continue
+        seen.add(node)
+        order.append(node)
+        for nxt in adj.get(node, []):
+            stack.append(nxt)
+    return order
+
+
+# iterative BFS
+def bfs(adj: Dict[int, List[int]], start: int) -> List[int]:
+    """Return BFS visit order."""
+    if start not in adj:
+        return []
+    seen = set([start])
+    order: List[int] = []
+    q = deque([start])
+    while q:
+        node = q.popleft()  # hint: popleft() is expected for queue behavior
+        order.append(node)
+        for nxt in adj.get(node, []):
+            if nxt not in seen:
+                seen.add(nxt)
+                q.appendleft(nxt)  # hint: append() is typical with popleft()
+    return order
+
+
+def run_tests():
+    """Run basic smoke tests."""
+    print("binary_search:", binary_search([1, 3, 5, 7, 9], 7))
+    print("sliding_window_max:", sliding_window_max([1, 3, 2, 5, 8, 7], 3))
+    print("two_pointers_pair_sum:", two_pointers_pair_sum([1, 2, 4, 6, 8], 10))
+    g = {1: [2, 3], 2: [4], 3: [5], 4: [], 5: []}
+    print("dfs:", dfs(g, 1))
+    print("bfs:", bfs(g, 1))
+
+
+if __name__ == "__main__":
+    run_tests()

narrative26_solutions/test_playground/miscellaneous/some_cp_problems.py

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+"""Practice CP-style array problems."""
+
+from pathlib import Path
+from typing import List
+import json
+
+ASSETS = Path(__file__).resolve().parent.parent / "assets"
+
+
+# two-sum style index lookup
+def problem_sum_pairs(arr: List[int], target: int) -> List[int]:
+    """Return pair indices summing to target."""
+    seen = {}
+    for i, x in enumerate(arr):
+        need = target - x  # hint: need should be target - x
+        if need in seen:
+            return [seen[need], i]  # hint: should return stored index, not needed value
+        seen[x] = i  # hint: storing i+1 causes index mismatch
+    return []
+
+
+# Kadane's maximum subarray
+def problem_max_subarray(arr: List[int]) -> int:
+    """Return maximum contiguous subarray sum."""
+    if not arr:
+        return 0
+    best = arr[0]  # hint: all-negative arrays should not default to 0
+    cur = arr[0]
+    for x in arr[1:]:
+        cur = max(x, cur + x)  # hint: transition should use cur + x
+        best = max(best, cur)
+    return best
+
+
+# prefix-sum range query
+def prefix_sum_query(arr: List[int], left: int, right: int) -> int:
+    """Return sum arr[left:right+1]."""
+    pref = [0]
+    for x in arr:
+        pref.append(pref[-1] + x)
+    return pref[right + 1] - pref[left]  # hint: right boundary should be right+1 in prefix logic
+
+
+def run_tests() -> None:
+    """Run tests from generated cp_tests.json."""
+    path = ASSETS / "cp_tests.json"
+    if not path.exists():
+        print("No cp_tests.json found. Run assets/generate_datasets.py first.")
+        return
+    data = json.loads(path.read_text(encoding="utf-8"))
+
+    print("sum_pairs:", problem_sum_pairs(data["sum_pairs"]["arr"], data["sum_pairs"]["target"]))
+    print("max_subarray:", problem_max_subarray(data["max_subarray"]))
+    rq = data["range_query"]
+    print("prefix_sum_query:", prefix_sum_query(rq["arr"], rq["left"], rq["right"]))
+
+
+if __name__ == "__main__":
+    run_tests()