Problem
The singleton pattern makes sure a class has exactly one instance that everyone shares, a common choice for application settings.
Simulate one shared configuration that starts empty. Process the operations in order:
set <key> <value>: store the value for the key (replacing any old value).get <key>: read the key's current value, ormissingif it was never set.
Because every caller uses the same instance, a value set by one operation is visible to every later get.
Implement shared_configuration(operations).
Input
operations: Strings in the two forms above. Keys and values contain no spaces.
Output
Return the results of the get operations, in order.
Constraints
1 ≤ number of operations ≤ 10,000
Keys and values have 1 to 20 characters
Examples
Input:
operations = ["set theme dark", "get theme", "get language"]
Expected output:
expected = ["dark", "missing"]Input:
std::vector<std::string> operations = {"set theme dark", "get theme", "get language"};
Expected output:
std::vector<std::string> expected = {"dark", "missing"};Input:
string[] operations = new string[] {"set theme dark", "get theme", "get language"};
Expected output:
string[] expected = new string[] {"dark", "missing"};Explanation
theme was set to dark; language was never set, so it is missing: ["dark", "missing"].
Input:
operations = ["set lang en", "set lang vi", "get lang"]
Expected output:
expected = ["vi"]Input:
std::vector<std::string> operations = {"set lang en", "set lang vi", "get lang"};
Expected output:
std::vector<std::string> expected = {"vi"};Input:
string[] operations = new string[] {"set lang en", "set lang vi", "get lang"};
Expected output:
string[] expected = new string[] {"vi"};Explanation
The second set replaces the first value in the same shared instance: ["vi"].
How to approach it
Try on your own first, then open one hint at a time.
Hint 1
All operations read and write the same single object.
Hint 2
A dictionary from key to value is enough to hold the settings.
Hint 3
A key that was never set must return the text missing.
Expected complexity
O(number of operations) time, O(number of keys) extra space
References
This challenge is adapted for CodeUtility. Follow the statement and constraints above.