leetcode 1656 - Design an Ordered Stream

https://leetcode.com/problems/design-an-ordered-stream/

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.

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class OrderedStream {
public:
OrderedStream(int n) {
chunks.resize(n+1, {false, ""});
}

vector<string> insert(int idKey, string value) {
chunks[idKey] = {false, value};

bool found_chunk = false;
if (idKey == 1 || chunks[idKey-1].first == true)
found_chunk = true;

vector<string> result;
if (found_chunk) {
int size = chunks.size();
while (idKey < size && chunks[idKey].first == false && !chunks[idKey].second.empty()) {
result.push_back(chunks[idKey].second);
chunks[idKey].first = true;
idKey++;
}
}

return result;
}

private:
vector<pair<bool, string>> chunks;
};

/**
* Your OrderedStream object will be instantiated and called as such:
* OrderedStream* obj = new OrderedStream(n);
* vector<string> param_1 = obj->insert(idKey,value);
*/