[数据结构与算法]2022-3-31 Leetcode 415.字符串相加

最终版，难度不大，魔鬼细节

class Solution {
public:
    string addStrings(string num1, string num2) {
        reverse(num1.begin(),num1.end());
        reverse(num2.begin(),num2.end());
        string ret;
        int i = 0;
        int len1 = num1.size();
        int len2 = num2.size();
        int carry = 0;
        while(i < len1 && i < len2){
            int a = num1[i] - '0';
            int b = num2[i] - '0';
            int sum = carry + a + b;
            ret += ((sum%10)+'0');
            carry = sum/10;
            i++;
        }
        string temp;
        if(i == len1){
            temp = num2.substr(i);
        }else if(i == len2){
            temp = num1.substr(i);
        }
        i = 0;
        int len = temp.size();
        while(i < len){
            if(carry == 0){
                string str = temp.substr(i);
                if(!str.empty())
                ret += str;
                //ret += temp.substr(i);
               // return ret;
               break;
            }
            else {
                int a = temp[i] - '0';
                int sum = a + carry;
                ret += (sum%10 +'0');
                carry = sum/10;
            }
            i++;
        }
        if(carry)
        ret += (carry +'0');
        reverse(ret.begin(),ret.end());
        return ret;
    }
};

第一版，想用库函数偷懒我输了

class Solution {
public:
    string addStrings(string num1, string num2) {
        long long int res = stoll(num1) + stoll(num2);
        return to_string(res);
    }
};

第二版，长度不一致的处理不好，里面有多处错误

string addStrings(string num1, string num2) {
        reverse(num1.begin(),num1.end());
        reverse(num2.begin(),num2.end());
        string ret;
        int i = 0;
        int len1 = num1.size();
        int len2 = num2.size();
        int carry = 0;
        while(i < len1 && i < len2){
            int a = num1[i] - '0';
            int b = num2[i] - '0';
            int sum = carry + a + b;
            ret += ((sum%10)+'0');
            carry = sum/10;
            i++;
        }
        string temp;
        if(i == len1){
            temp = num2.substr(i);
        }else if(i == len2){
            temp = num2.substr(i);
        }
        i = 0;
        int len = temp.size();
        while(i < len){
            if(carry == 0){
                ret += temp.substr(i);
               // return ret;
               break;
            }
            else {
                int a = temp[i] - '0';
                int sum = a + carry;
                ret += (sum%10 - '0');
                carry = sum/10;
            }
        }
        if(carry)
        ret += (carry -'0');
        reverse(ret.begin(),ret.end());
        return ret;
    }