sum-of-two-integers.md

Problem

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

Example 1:

Input: a = 1, b = 2
Output: 3

Example 2:

Input: a = -2, b = 3
Output: 1

Attempt

• Bitwise Arithmetic Operation
• Explanation

/**
 * @param {number} a
 * @param {number} b
 * @return {number}
 */
var getSum = function(a, b) {
    let a_bit = (a >>> 0).toString(2)
    let b_bit = (b >>> 0).toString(2)
    
    var sum = a^b; //XOR
    var carry = (a&b) << 1; //Left shift a AND b
    
    if(sum & carry){
        return getSum(sum,carry)
    }
    else {
        return sum ^ carry;
    }
};

Result

• Runtime: 52 ms
• Memory Usage: 33.9 MB

OR

/**
 * @param {number} a
 * @param {number} b
 * @return {number}
 */
var getSum = function(a, b) {
     return b==0? a:getSum(a^b, (a&b)<<1);
};

Result

• Runtime: 60 ms
• Memory Usage: 33.8 MB