题解 | #大数加法#

function solve( s , t ) {

let sum = "";
let i = s.length - 1, j = t.length - 1;
let carry = 0;

while(i >= 0 || j >= 0){
    //这里采用的是取反运算符，当s或者t角标越界时，结果是undefined，~~undefined = 0
    // +undefined = NaN， parseInt(undefined) = NaN
    
    let temp = ~~s[i] + ~~t[j] + carry;
    
    if(temp >= 10){
        temp %= 10;
        carry = 1;
    }else{
        carry = 0;  //需要把carry置为0，不然会影响后面的值
    }
    
    sum = temp + sum;
    
    i--;
    j--;
}

if(carry == 1) sum = carry + sum;

return sum

}

module.exports = { solve : solve };