1024. 科学计数法 (20)

#include<iostream>
#include<vector>
#include<sstream>
using namespace std;

int main()
{
    string a;
    getline(cin,a);
    //提取出基本数字num，指数e，指数的正负x
    bool isPositive = true;
    if(a[0]=='-'){
        isPositive = false;
        cout << "-";
    }
    a = a.substr(1);
    int numE = a.find('E');
    string num = a.substr(0,numE);
    char x = a[numE+1];
    string E = a.substr(numE+2,a.length()-numE-1);
    stringstream ss;
    int e;
    ss << E;
    ss >> e;
    //灵活利用substr分割num
    if(e == 0){
        cout <<num<<endl;
        return 0;
    }
    if(x == '-'){
        string cc = "0.";
        e--;
        while (e--) {
            cc = cc + '0';
        }
        cc = cc + num[0] + num.substr(2);
        cout << cc << endl;
    }
    if(x == '+'){
        if(e<num.length()-2){
            string cc;
         cc =num[0]+num.substr(2,e)+'.'+num.substr(2+e,num.length()-2-e);
            cout << cc << endl;
        }else {
            string cc;
            cc = num[0]+num.substr(2);
            int k = e - (num.length() - 2);
            while (k--) {
                cc += '0';
            }
            cout << cc << endl;
        }
    }
    return 0;
}