技術標籤：PAT 甲級

（C++程式碼）轉載連結：https://blog.csdn.net/qq_36721800/article/details/104649796

牛客連結：https://www.nowcoder.com/practice/ddec753f446e4ba4944e35378ba635c8?tpId=61&tqId=29551&tPage=3&ru=/kaoyan/retest/1002&qru=/ta/pku-kaoyan/question-ranking

java程式碼

public class Solution extends Calculator{
    @Override
 

    public Object add(Object leftValue, Object rightValue) {

        String s1 = leftValue.toString();
        String s2 = rightValue.toString();
        if (s1.indexOf(".")==-1 && s2.indexOf(".")==-1){
            //如果不含小數，普通的大整數加法
            return add(s1,s2);
        }
 
else{
            return addFloatNum(s1,s2);
        }
    }



    public String addFloatNum(String num1, String num2) {//兩個浮點大數相加，小數點位數任意
        String result = "";
        int pos1,pos2,len1,len2;
        len1 = num1.length();
        len2 = num2.length();
        pos1 = num1.indexOf('.'
 
);
        pos2 = num2.indexOf('.');

        //分別剝離兩個數的整數和小數部分
        String num1a = num1.substring(0, pos1);
        String num1b = num1.substring(pos1+1, len1);
        String num2a = num2.substring(0, pos2);
        String num2b = num2.substring(pos2+1, len2);

        //整數部分相加
        String rsOne = addBigInt(num1a, num2a);
        //小數位對齊，不足的補0
        int i,nZeroes,maxLen;
        maxLen = (num1b.length()>num2b.length()) ? num1b.length() : num2b.length();
        if (num1b.length()>num2b.length()) {//第一個數的小數部分長,則第二個補不足的0
            nZeroes = num1b.length() - num2b.length();//待補的0的個數
            for (i = 0; i < nZeroes; ++i) {
                num2b += '0';
            }
        } else if(num2b.length() > num1b.length()) {//第二個數的小數部分長,則第一個補不足的0
            nZeroes = num2b.length() - num1b.length();//待補的0的個數
            for (i = 0; i < nZeroes; ++i) {
                num1b += '0';
            }
        }

        //小數位對齊準備完畢，進行小數部分相加
        String rsTwo = addBigInt(num1b, num2b);
        if (rsTwo.length() > maxLen)
        {
            //說明有進位, 剝離第一位進位，加到整數部分去
            String nAddOn = rsTwo.substring(0,1);
            rsOne = addBigInt(rsOne, nAddOn);
            rsTwo = rsTwo.substring(1,rsTwo.length());
        }

        //兩部分結果拼湊起來
        StringBuilder sb = new StringBuilder(rsOne);
        sb.append(".");
        sb.append(rsTwo);
        result = sb.toString();
        return result;
    }

    public String addBigInt(String num1, String num2) {
        //大整數相加
        String result = "";
        int len1 = num1.length();
        int len2 = num2.length();
        int nAddOn = 0;
        int i,j,n1,n2,sum;
        StringBuilder sb = new StringBuilder();
        for (i = len1 - 1,j = len2 - 1 ; i >= 0 && j >= 0; --i,--j)
        {
            n1 = num1.charAt(i) - '0';
            n2 = num2.charAt(j) - '0';
            sum = n1 + n2 + nAddOn;
            if (sum >= 10) {
                nAddOn = 1;
            }else {
                nAddOn = 0;
            }
            sb.append(sum % 10);
        }
        if (len1 > len2) {
            for (; i >= 0; --i) {
                n1 = num1.charAt(i) - '0';
                sum = n1 + nAddOn;
                if (sum >= 10) {
                    nAddOn = 1;
                }else{
                    nAddOn = 0;
                }
                sb.append(sum % 10);
            }
        }else if (len2 > len1) {
            for (; j >= 0; --j) {
                n2 = num2.charAt(j) - '0';
                sum = n2 + nAddOn;
                if (sum >= 10) {
                    nAddOn = 1;
                }else {
                    nAddOn = 0;
                }
                sb.append(sum % 10);
            }
        }
        if (nAddOn > 0)
        {
            sb.append(nAddOn);
        }
        sb.reverse();
        result = sb.toString();
        return result;
    }


}