两个长数字相加

浅浅的花香味﹌ 2022-01-07 21:13 258阅读 0赞

## 1.编程题目 ##

题目：要实现两个百位长的数字直接相加  
分析：因为数字太长所以无法直接相加，所以采用按位相加，然后组装的方式。（注意进位）

## 2.编程实现 ##

package com.sino.daily.code_2019_6_29;
    
    import org.apache.commons.lang3.StringUtils;
    
    /** * create by 2019-06-29 19:03 * * @author caogu */
    public class Main { 
        public static void main(String[] args) { 
    
            String num1 = new String("1111111122323233333333388");
            String num2 = new String("1111111122323233333333");
    
            Main m = new Main();
            System.out.println(m.sum(num1, num2));
        }
    
        private String sum(String num1, String num2) { 
            String maxNum = num1.length() > num2.length() ? num1 : num2;
            String minNum = num1.length() < num2.length() ? num1 : num2;
    
            //前面用0补齐
            minNum = StringUtils.repeat("0", maxNum.length() - minNum.length()) + minNum;
    
            System.out.println(maxNum);
            System.out.println(minNum);
            System.out.println(StringUtils.repeat("-", maxNum.length()) + " +");
    
            //按位相加，向上进位
            StringBuilder sum = new StringBuilder();
            int carryBit = 0;
            for (int i = maxNum.length() - 1; i >= 0; i--) { 
                int bitNum1 = Integer.parseInt(String.valueOf(maxNum.charAt(i)));
                int bitNum2 = Integer.parseInt(String.valueOf(minNum.charAt(i)));
    
                int bitSum = bitNum1 + bitNum2 + carryBit;
                sum.append(bitSum % 10);
    
                carryBit = bitSum / 10;
            }
    
            //处理最高位
            if (carryBit != 0) { 
                sum.append(carryBit);
            }
    
            // 字符串反转输出
            return sum.reverse().toString();
        }
    }

结果如下：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9qaWVuaXlpbWlhby5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9qaWVuaXlpbWlhby5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70]: /images/20211220/5da9599b4e7b472386f341d63b94d8c3.png