Added barcode_validator.py (TheAlgorithms#6771)

* Update README.md

Added Google Cirq references

* Create barcode_validator.py

Barcode/EAN validator

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* Update barcode_validator.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>

quantum/README.md

@@ -6,10 +6,18 @@ Started at https://github.com/TheAlgorithms/Python/issues/1831
 * Google: https://research.google/teams/applied-science/quantum
 * IBM: https://qiskit.org and https://github.com/Qiskit
 * Rigetti: https://rigetti.com and https://github.com/rigetti
+* Zapata: https://www.zapatacomputing.com and https://github.com/zapatacomputing
 
 ## IBM Qiskit
 - Start using by installing `pip install qiskit`, refer the [docs](https://qiskit.org/documentation/install.html) for more info.
 - Tutorials & References
   - https://github.com/Qiskit/qiskit-tutorials
   - https://quantum-computing.ibm.com/docs/iql/first-circuit
   - https://medium.com/qiskit/how-to-program-a-quantum-computer-982a9329ed02
+
+## Google Cirq
+- Start using by installing `python -m pip install cirq`, refer the [docs](https://quantumai.google/cirq/start/install) for more info.
+- Tutorials & references
+  - https://github.com/quantumlib/cirq
+  - https://quantumai.google/cirq/experiments
+  - https://tanishabassan.medium.com/quantum-programming-with-google-cirq-3209805279bc

strings/barcode_validator.py

@@ -0,0 +1,88 @@
+"""
+https://en.wikipedia.org/wiki/Check_digit#Algorithms
+"""
+
+
+def get_check_digit(barcode: int) -> int:
+    """
+    Returns the last digit of barcode by excluding the last digit first
+    and then computing to reach the actual last digit from the remaining
+    12 digits.
+
+    >>> get_check_digit(8718452538119)
+    9
+    >>> get_check_digit(87184523)
+    5
+    >>> get_check_digit(87193425381086)
+    9
+    >>> [get_check_digit(x) for x in range(0, 100, 10)]
+    [0, 7, 4, 1, 8, 5, 2, 9, 6, 3]
+    """
+    barcode //= 10  # exclude the last digit
+    checker = False
+    s = 0
+
+    # extract and check each digit
+    while barcode != 0:
+        mult = 1 if checker else 3
+        s += mult * (barcode % 10)
+        barcode //= 10
+        checker = not checker
+
+    return (10 - (s % 10)) % 10
+
+
+def is_valid(barcode: int) -> bool:
+    """
+    Checks for length of barcode and last-digit
+    Returns boolean value of validity of barcode
+
+    >>> is_valid(8718452538119)
+    True
+    >>> is_valid(87184525)
+    False
+    >>> is_valid(87193425381089)
+    False
+    >>> is_valid(0)
+    False
+    >>> is_valid(dwefgiweuf)
+    Traceback (most recent call last):
+    ...
+    NameError: name 'dwefgiweuf' is not defined
+    """
+    return len(str(barcode)) == 13 and get_check_digit(barcode) == barcode % 10
+
+
+def get_barcode(barcode: str) -> int:
+    """
+    Returns the barcode as an integer
+
+    >>> get_barcode("8718452538119")
+    8718452538119
+    >>> get_barcode("dwefgiweuf")
+    Traceback (most recent call last):
+    ...
+    ValueError: Barcode 'dwefgiweuf' has alphabetic characters.
+    """
+    if str(barcode).isalpha():
+        raise ValueError(f"Barcode '{barcode}' has alphabetic characters.")
+    elif int(barcode) < 0:
+        raise ValueError("The entered barcode has a negative value. Try again.")
+    else:
+        return int(barcode)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+    """
+    Enter a barcode.
+
+    """
+    barcode = get_barcode(input("Barcode: ").strip())
+
+    if is_valid(barcode):
+        print(f"'{barcode}' is a valid Barcode")
+    else:
+        print(f"'{barcode}' is NOT is valid Barcode.")