371. Sum of Two Integers - python3

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

이 문제를 낸 의도가 무엇일까...

My Answer 1: Accepted (Runtime: 24 ms - 93.30% / Memory Usage: 14.3 MB - 37.83%)

class Solution:
    def getSum(self, a: int, b: int) -> int:
        twoint = [a,b]
        return sum(twoint)

이거 거의 창의력 문제 아닌지..
+- 연산자 쓰지 말래서 그냥 sum 함수 썼다.

sum 은 리스트, 튜플... 에 사용
리스트로 쓰나 튜플로 쓰나 런타임은 비슷하다

BITWISE OPERATIONS

Solution 1: Runtime: 28 ms - 73.68% / Memory Usage: 14.1 MB - 63.51%

class Solution:
    def getSum(self, a: int, b: int) -> int:
        ## RC ##
        ## APPROACH : BITWISE OPERATIONS ##
        ## LOGIC ##
        #   1. For any two numbers, if their binary representations are completely opposite, then XOR operation will directly produce sum of numbers ( in this case carry is 0 )
        #   2. what if the numbers binary representation is not completely opposite, XOR will only have part of the sum and remaining will be carry, which can be produced by and operation followed by left shift operation.
        #   3. For Example 18, 13 => 10010, 01101 => XOR => 11101 => 31 (ans found), and operation => carry => 0
        #   4. For Example 7, 5
        #   1 1 1                   1 1 1
        #   1 0 1                   1 0 1
        #   -----                   -----
        #   0 1 0   => XOR => 2     1 0 1  => carry => after left shift => 1 0 1 0
        #   2                                                              10
        # now we have to find sum of 2, 10 i.e a is replace with XOR result and b is replaced wth carry result
        # similarly repeating this process till carry is 0
        #   steps will be 7|5 => 2|10 => 8|4  => 12|0
        
		## TIME COMPLEXITY : O(1) ##
		## SPACE COMPLEXITY : O(1) ##
        
        # 32 bit mask in hexadecimal
        mask = 0xffffffff # (python default int size is not 32bit, it is very large number, so to prevent overflow and stop running into infinite loop, we use 32bit mask to limit int size to 32bit )
        while(b & mask > 0):
            carry = (a & b) << 1
            a = a ^ b
            b = carry
        return (a & mask) if b > 0 else a

비트연산자 트라우마인데... 이걸 쓰는게 목적이었나봅니다

비트연산자 공부하기!!!