30 Days of Code [Day 9]

22 Aug 2021

QUESTION : 43. Multiply Strings

#define vi vector<int>
#define pii pair<int, int>
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define fo(i,s,n) for(int i=s;i<n;++i)
#define of(i,s,n) for(int i=s-1;i>=n;--i)
#define fv(V) for( auto &it : V )
class Solution {
public:
    string multiply(string num1, string num2) {
        if(num1 == "0" || num2 == "0") return "0";
        int n = num1.size();
        int m = num2.size();
        vi v(n+m, 0);
        int pw = 0;
        of(i,n,0){
            int carry = 0;
            int k = v.size()-1-pw;
            of(j,m,0){
                int s = (num1[i] - '0')*(num2[j] - '0') + carry + v[k];
                
                carry = s/10;
                v[k] = s%10;
                k--;
            }
            if(carry > 0) v[k] += carry;
            pw ++;
        }
        string res = "";
        bool f = false;
        fv(v){
            if(!it && !f) continue;
            else{
                res += to_string(it);
                f = true;
            }
        }
        return res;
    }
};