LC_371_SumWithoutArithmeticOperatorsNegative.cpp

/* https://leetcode.com/problems/sum-of-two-integers/
 * Given two integers a and b, return the sum of the two integers without using the operators + and -.
 */
 
class Solution {
public:
    int getSum(int a, int b) {
        
        // return a+b;
        /* 
            //Iterative APPROACH of ++ --
            if(b>0){
                while(b!=0){
                    a++;
                    b--;
                }
            }
            else if(b<0){
                while(b!=0){
                    a--;
                    b++;
                }
            }
            return a;
    
        */
        /* 
        //HALF ADDER APPROACH and Bit Manipulation
            int sum, carry;
            while(b!=0){
                sum = a^b;          // sum without carries
                carry = a & b;      //shows each location where carry is needed
                a = sum;
                b = ((unsigned int)carry)<<1;   // shift the carry left one column for adding
            }//while loop

              return a;
       */  
        
        int sum=a;
        unsigned int carry = b; // sirf unsigned int likhne se purana code chlne lga wow.
        
        while(carry>0)
        {
            sum = a ^ b; // sum of bits of a and b where atleast one is not set
            carry = (a & b); // common set bits of a and b
            // cout<<"sum "<<sum;
            // cout<<"   c "<<carry<<endl;
            carry <<= 1; // shift carry one bit to add with
            a = sum;
            b = carry;
        }
        
        return sum;
        
        //Power and LOG APPROACH
        if(a == 0)
            return b;
        if(b == 0)
            return a;
        
        const auto e_a = exp(a);
        const auto e_b = exp(b);
        const auto e_ab = e_a * e_b;
        return static_cast<int>(log(e_ab));
    }
};