This code contains a class definition (`MyClass`) that implements a...

This code contains a class definition (MyClass) that implements a basic mechanism for finding two indices of numbers from a list that add up to a specified target value.

Here is a step-by-step breakdown of what the code does:

Class Definition: MyClass

1. Attributes:

   • self.lookup: A dictionary used to store the values from self.vals as keys and their corresponding indices as values (for fast lookup).
   • self.vals: A list of numbers provided during initialization.

2. Methods:

   • __init__(self, vals): The constructor method initializes the lookup dictionary as empty and assigns the provided vals list to the self.vals attribute.
   • method(self, target): This method performs the following:
     • Iterates through the list self.vals using both the indices (i) and the values (num from self.vals[i]).
     • For each number num in the list, it calculates the difference (target - num).
     • Checks if the difference (target - num) exists in the self.lookup dictionary:
       • If it does, it means the current number num and a previously seen number in self.vals (stored in self.lookup) add up to the target. It then returns the pair of indices as a tuple: the index of the previously seen number and the current index (from lookup[target - num] and i).
       • If it does not, the current number num is stored in the self.lookup dictionary as a key, with the corresponding index i as its value.

Example Execution

The provided statements execute as follows:

• a = MyClass([10, 20, 10, 40]): Initializes an instance a of MyClass with the list [10, 20, 10, 40].

• res1 = a.method(50)[0]:

  • Calls a.method(50) to find two indices of numbers that sum up to 50:
    • Iteration 1: i = 0, num = 10: Difference 50 - 10 = 40 is not in self.lookup. Adds {10: 0} to lookup.
    • Iteration 2: i = 1, num = 20: Difference 50 - 20 = 30 is not in self.lookup. Adds {10: 0, 20: 1}.
    • Iteration 3: i = 2, num = 10: Difference 50 - 10 = 40 is not in self.lookup. Adds {10: 2, 20: 1} (overwriting index of previous 10).
    • Iteration 4: i = 3, num = 40: Difference 50 - 40 = 10 is in self.lookup. Returns (2, 3) (indices of 10 and 40).
  • res1 = 2 (the first index of the pair (2, 3)).

• res2 = a.method(30)[1]:

  • Calls a.method(30) to find two indices of numbers that sum up to 30:
    • Notes that the same self.lookup from the previous call ({10: 2, 20: 1}) persists.
    • Iteration 1: Picks the indices for 20 and 10.
    • Returns `(1 Paint new state