【LeetCode】415. Add Strings

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

Note:

The length of both num1 and num2 is < 5100.
Both num1 and num2 contains only digits 0-9.
Both num1 and num2 does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.

字符串相加。

class Solution {public:    string addStrings(string num1, string num2) {        string ans;        reverse(num1.begin(),num1.end());        reverse(num2.begin(),num2.end());        int i=0,len1=num1.size();        int j=0,len2=num2.size();        int t=0;        while(i<len1&&j<len2){            int sum=t+(num1[i]-'0')+(num2[j]-'0');            ans=(char)(sum%10+'0')+ans;            t=sum/10;            i++;j++;        }        while(i<len1){            int sum=t+(num1[i]-'0');            ans=(char)(sum%10+'0')+ans;            t=sum/10;            i++;        }         while(j<len2){            int sum=t+(num2[j]-'0');            ans=(char)(sum%10+'0')+ans;            t=sum/10;            j++;        }        if(t)ans='1'+ans;        return ans;    }};