1073 Scientific Notation （PAT甲级）

1073. Scientific Notation (20)-PAT甲级真题_柳婼的博客-CSDN博客

先贴柳婼的解题，她的方法感觉不容易有疏漏。我的方法比较容易忽略37-42行的代码，也就是当还存在分数部分时，怎么处理的问题。

#include 
#include 

int main(){
    std::string str;
    int pos, k;
    std::cin >> str;
    std::cout << (str[0] == '+' ? "" : "-");
    str = str.substr(1);
    pos = str.find("E");
    k = std::stoi(str.substr(pos + 1));
    str = str.substr(0, pos);
    if(k < 0){
        std::cout << "0.";
        for(int i = 0; i < -k - 1; ++i){
            std::cout << "0";
        }
        for(int i = 0; i < str.size(); ++i){
            if(str[i] != '.'){
                std::cout << str[i];
            }
        }
    } else if(k == 0){
        std::cout << str;
    } else{
        bool flag = true;
        for(int i = 1; i <= k; ++i){
            if(i + 1 < str.size()){
                str[i] = str[i + 1];
            } else if(i + 1 == str.size()){
                str[i] = '0';
                flag = false;
            } else{
                str += "0";
            }
        }
        if(flag){
            str[k + 1] = '.';
            if(str[str.size() - 1] == '.'){
                str = str.substr(0, str.size() - 1);
            }
        }
        std::cout << str;
    }
    return 0;
}

题目如下：

Scientific notation is the way that scientists easily handle very large numbers or very small numbers. The notation matches the regular expression [+-][1-9].[0-9]+E[+-][0-9]+ which means that the integer portion has exactly one digit, there is at least one digit in the fractional portion, and the number and its exponent's signs are always provided even when they are positive.

Now given a real number A in scientific notation, you are supposed to print A in the conventional notation while keeping all the significant figures.

Input Specification:

Each input contains one test case. For each case, there is one line containing the real number A in scientific notation. The number is no more than 9999 bytes in length and the exponent's absolute value is no more than 9999.

Output Specification:

For each test case, print in one line the input number A in the conventional notation, with all the significant figures kept, including trailing zeros.

Sample Input 1:

+1.23400E-03

Sample Output 1:

0.00123400

Sample Input 2:

-1.2E+10

Sample Output 2:

-12000000000