415. Add Strings

 

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

Note:

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

 

这道题让我们求两个字符串的相加,之前 LeetCode 出过几道类似的题目,比如二进制数相加,还有链表相加,或是字符串加1,基本思路很类似,都是一位一位相加,然后算和算进位,最后根据进位情况看需不需要补一个高位,难度不大,参见代码如下:

 

class Solution {
public:
    string addStrings(string num1, string num2) {
        string res = "";
        int m = num1.size(), n = num2.size(), i = m - 1, j = n - 1, carry = 0;
        while (i >= 0 || j >= 0) {
            int a = i >= 0 ? num1[i--] - '0' : 0;
            int b = j >= 0 ? num2[j--] - '0' : 0;
            int sum = a + b + carry;
            res.insert(res.begin(), sum % 10 + '0');
            carry = sum / 10;
        }
        return carry ? "1" + res : res;
    }
};

 

讨论:由热心网友 zzcRq1 提供了一种 Follow up,当字符串中有小数点和负号怎么处理。博主稍微想了一下,感觉还挺麻烦的,首先应该判断有几个负号,若只有一个,则是减法,而若负号的个数是0个或者是2个的时候,则还是加法。而小数点的处理就是将小数部分和整数部分拆分出来,分别进行加法和减法,最后再拼接上去,感觉大概应该是这样处理的,感兴趣的童鞋可以写个代码实现一样,可以在评论区贴上你的代码哈~

 

Github 同步地址:

https://github.com/grandyang/leetcode/issues/415

 

类似题目:

Add Digits

Add Binary

Add Two Numbers

Multiply Strings

Add to Array-Form of Integer

 

参考资料:

https://leetcode.com/problems/add-strings/

https://leetcode.com/problems/add-strings/discuss/90453/C%2B%2B_Accepted_13ms

https://leetcode.com/problems/add-strings/discuss/90436/Straightforward-Java-8-main-lines-25ms

 

LeetCode All in One 题目讲解汇总(持续更新中…)


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