leetcode 415. 字符串相加（Java版）

约定不等于承诺〃 2023-01-17 07:46 128阅读 0赞

## 题目 ##

[https://leetcode-cn.com/problems/add-strings/][https_leetcode-cn.com_problems_add-strings]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_1_color_FFFFFF_t_70]

## 题解 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 代码 ##

/** * 给定两个字符串形式的非负整数 num1 和 num2 ，计算它们的和。 */
    public class Solution { 
        public static String addStrings(String num1, String num2) { 
            char[] c1 = num1.toCharArray();
            char[] c2 = num2.toCharArray();
            if (c1.length >= c2.length) {  // 假设 c2 位数多。否则交换 c1 c2 从而使其符合假设。
                c1 = num2.toCharArray();
                c2 = num1.toCharArray();
            }
            int maxLen = c2.length;
            int[] c3 = new int[maxLen + 1];
            int[] c1_copy = new int[maxLen + 1];
            int[] c2_copy = new int[maxLen + 1];
            for (int i = 0; i < c1.length; i++) {  // 将 c1_copy 填充至与 c3 相同长度
                c1_copy[maxLen - i] = c1[c1.length - i - 1] - '0';
            }
            for (int i = 0; i < c2.length; i++) {  // 将 c2_copy 填充至与 c3 相同长度
                c2_copy[maxLen - i] = c2[c2.length - i - 1] - '0';
            }
            int carry = 0;
            for (int i = maxLen; i >= 0; i--) {  // 逐位相加
                int sum = c1_copy[i] + c2_copy[i] + carry;
                if (sum >= 10) { 
                    c3[i] = sum - 10;
                    carry = 1;
                } else { 
                    c3[i] = sum;
                    carry = 0;
                }
            }
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i <= maxLen; i++) { 
                if (i != 0 || c3[i] != 0) sb.append(c3[i]);
            }
            return sb.toString();
        }
    
        public static void main(String[] args) { 
            System.out.println(addStrings("11", "123"));
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode-cn.com_problems_add-strings]: https://leetcode-cn.com/problems/add-strings/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_1_color_FFFFFF_t_70]: /images/20221021/ab3ec72807a34074a7afb92bce0e15a4.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20221021/0affedf4ebc84791b097178c3835ffee.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20221021/0002af4d91a347cda0a2d16313581ff5.png