New: Added proof of work(PoW) (#11946)

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* updating DIRECTORY.md

---------

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

Author: 3 people

DIRECTORY.md

@@ -110,6 +110,8 @@
 ## [Blockchain](blockchain)
   * [Diophantine Equation](blockchain/diophantine_equation.py)
   * [Merkle Tree](blockchain/merkle_tree.py)
+  * [Proof Of Stake](blockchain/proof_of_stake.py)
+  * [Proof Of Work](blockchain/proof_of_work.py)
   * [Simple Blockchain](blockchain/simple_blockchain.py)
   * [Simple Proof Of Work](blockchain/simple_proof_of_work.py)
 

blockchain/proof_of_stake.py

@@ -0,0 +1,40 @@
+import random
+
+
+class Validator:
+    def __init__(self, name: str, stake: int) -> None:
+        """
+        Initializes a new validator with a given name and stake.
+
+        Args:
+            name (str): The name of the validator.
+            stake (int): The amount of stake the validator has.
+        """
+        self.name = name
+        self.stake = stake
+
+
+def choose_validator(validators: list[Validator]) -> Validator:
+    """
+    Selects a validator to create the next block based on the weight of their stake.
+
+    The higher the stake, the greater the chance to be selected.
+
+    Args:
+        validators (list[Validator]): A list of Validator objects.
+
+    Returns:
+        Validator: The selected validator based on weighted random selection.
+
+    Example:
+        >>> validators = [Validator("Alice", 50), Validator("Bob", 30)]
+        >>> chosen = choose_validator(validators)
+        >>> isinstance(chosen, Validator)
+        True
+    """
+    total_stake = sum(v.stake for v in validators)
+    weighted_validators = [(v, v.stake / total_stake) for v in validators]
+    selected = random.choices(
+        [v[0] for v in weighted_validators], weights=[v[1] for v in weighted_validators]
+    )
+    return selected[0]

blockchain/proof_of_work.py

@@ -0,0 +1,29 @@
+import hashlib
+
+
+def proof_of_work(difficulty: int) -> int:
+    """
+    Simulates a Proof of Work mining process.
+
+    The miner must find a nonce such that the hash of the nonce starts
+    with a specific number of leading zeros (difficulty).
+
+    Args:
+        difficulty (int): The number of leading zeros required in the hash.
+
+    Returns:
+        int: The nonce value that solves the puzzle.
+
+    Example:
+        >>> result = proof_of_work(2)  # Difficulty of 2 should be fast
+        >>> isinstance(result, int)
+        True
+    """
+    prefix = "0" * difficulty
+    nonce = 0
+
+    while True:
+        hash_result = hashlib.sha256(f"{nonce}".encode()).hexdigest()
+        if hash_result.startswith(prefix):
+            return nonce
+        nonce += 1