larger-number-add/src/index.js

resolve large number plus

export default function add(a, b) {
    let i = a.length - 1;
    let j = b.length - 1;

    let carry = 0;
    let ret = '';
    while (i >= 0 || j >= 0) {
        let x = 0;
        let y = 0;
        let sum;

        if (i >= 0) {
            x = a[i] - '0';
            i --;
        }

        if (j >= 0) {
            y = b[j] - '0';
            j --;
        }

        sum = x + y + carry;

        if (sum >= 10) {
            carry = 1;
            sum -= 10;
        } else {
            carry = 0;
        }
        
        ret = sum + ret;
    }

    if (carry) {
        ret = carry + ret;
    }

    return ret;
}

// add('998', '2');
// add('2', '998');
// add('123', '321');
// add ('4', '1000000000000000000000000000')