算法-字符串-字符串相加

此题与链表相加有异曲同工之妙

class Solution {
    
    
    public String addStrings(String num1, String num2) {
    
    
        if(num1 == "0") {
    
    
            return num2;
        }
        if(num2 == "0") {
    
    
            return num1;
        }

        int i = num1.length() - 1;
        int j = num2.length() - 1;
        int carry = 0;
        int sum = 0;
        String str = "";
        while(i >= 0 || j >= 0 || carry != 0) {
    
    
            int a = i < 0? 0 : num1.charAt(i) - '0';//将字符转化为整数
            int b = j < 0? 0 : num2.charAt(j) - '0';

            sum = a + b + carry;

            carry = sum / 10;//获取进位
            sum = sum % 10;//获取各位

            str = sum + str;
            i--;
            j--;
        }

        return str;
    }
}

class Solution {
    
    
    public String addStrings(String num1, String num2) {
    
    
        int i = num1.length() - 1, j = num2.length() - 1, add = 0;
        StringBuffer ans = new StringBuffer();
        while (i >= 0 || j >= 0 || add != 0) {
    
    
            int x = i >= 0 ? num1.charAt(i) - '0' : 0;
            int y = j >= 0 ? num2.charAt(j) - '0' : 0;
            int result = x + y + add;
            ans.append(result % 10);
            add = result / 10;
            i--;
            j--;
        }
        // 计算完以后的答案需要翻转过来
        ans.reverse();
        return ans.toString();
    }
}

作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/add-strings/solution/zi-fu-chuan-xiang-jia-by-leetcode-solution/
来源：力扣（LeetCode）
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