Introduction

In this blog post, we will explore how to solve the LeetCode problem "1656" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

There is a stream of n (idKey, value) pairs arriving in an arbitrary order, where idKey is an integer between 1 and n and value is a string. No two pairs have the same id. Design a stream that returns the values in increasing order of their IDs by returning a chunk (list) of values after each insertion. The concatenation of all the chunks should result in a list of the sorted values. Implement the OrderedStream class: OrderedStream(int n) Constructs the stream to take n values. String[] insert(int idKey, String value) Inserts the pair (idKey, value) into the stream, then returns the largest possible chunk of currently inserted values that appear next in the order. Example: Input ["OrderedStream", "insert", "insert", "insert", "insert", "insert"] [[5], [3, "ccccc"], [1, "aaaaa"], [2, "bbbbb"], [5, "eeeee"], [4, "ddddd"]] Output [null, [], ["aaaaa"], ["bbbbb", "ccccc"], [], ["ddddd", "eeeee"]] Explanation // Note that the values ordered by ID is ["aaaaa", "bbbbb", "ccccc", "ddddd", "eeeee"]. OrderedStream os = new OrderedStream(5); os.insert(3, "ccccc"); // Inserts (3, "ccccc"), returns []. os.insert(1, "aaaaa"); // Inserts (1, "aaaaa"), returns ["aaaaa"]. os.insert(2, "bbbbb"); // Inserts (2, "bbbbb"), returns ["bbbbb", "ccccc"]. os.insert(5, "eeeee"); // Inserts (5, "eeeee"), returns []. os.insert(4, "ddddd"); // Inserts (4, "ddddd"), returns ["ddddd", "eeeee"]. // Concatentating all the chunks returned: // [] + ["aaaaa"] + ["bbbbb", "ccccc"] + [] + ["ddddd", "eeeee"] = ["aaaaa", "bbbbb", "ccccc", "ddddd", "eeeee"] // The resulting order is the same as the order above. Constraints: 1 <= n <= 1000 1 <= id <= n value.length == 5 value consists only of lowercase letters. Each call to insert will have a unique id. Exactly n calls will be made to insert.

Explanation

Here's an efficient solution to the problem:

• Use an Array for Storage: Store the incoming values in an array (or list in Python) indexed by their idKey. This allows for direct access and insertion in O(1) time on average.
• Maintain a Pointer: Keep a pointer to track the next expected idKey. After each insertion, advance the pointer as far as possible while values exist in the array.

• Return a Chunk: After advancing the pointer, create and return a list containing the values of the chunk that was identified.

• Runtime & Space Complexity: The runtime complexity is O(n) for the entire sequence of insert operations (O(1) for each insert operation on average, excluding the chunk generation) and O(n) for storage, where n is the maximum idKey.

Code

    class OrderedStream:

    def __init__(self, n: int):
        self.stream = [None] * (n + 1)  # 1-indexed
        self.ptr = 1
        self.n = n

    def insert(self, idKey: int, value: str) -> list[str]:
        self.stream[idKey] = value
        chunk = []
        while self.ptr <= self.n and self.stream[self.ptr] is not None:
            chunk.append(self.stream[self.ptr])
            self.ptr += 1
        return chunk

# Example usage (as in the problem description):
# os = OrderedStream(5)
# print(os.insert(3, "ccccc"))
# print(os.insert(1, "aaaaa"))
# print(os.insert(2, "bbbbb"))
# print(os.insert(5, "eeeee"))
# print(os.insert(4, "ddddd"))