1024 科学计数法

思路：模拟题，交了错，错了改最后写的丑了点，先判断一下正负号，然后第一个符号位到E之间的数直接用，第二个符号位到结尾确定小数点的位置

#pragma GCC optimize(2)
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <set>
#include<iostream>
#include<vector>
#include<queue>
#include<map>
#include<stack>
#include<iomanip>
//#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define SIS std::ios::sync_with_stdio(false)
#define space putchar(' ')
#define enter putchar('\n')
#define lson root<<1
#define rson root<<1|1
typedef pair<int,int> PII;
const int mod=1e9+7;
const int N=2e6+10;
const int M=1e3+10;
const int inf=0x7f7f7f7f;
const int maxx=2e5+7;
const double eps=1e-6;
int gcd(int a,int b)
{
    return b==0?a:gcd(b,a%b);
}

ll lcm(ll a,ll b)
{
    return a*(b/gcd(a,b));
}

template <class T>
void read(T &x)
{
    char c;
    bool op = 0;
    while(c = getchar(), c < '0' || c > '9')
        if(c == '-')
            op = 1;
    x = c - '0';
    while(c = getchar(), c >= '0' && c <= '9')
        x = x * 10 + c - '0';
    if(op)
        x = -x;
}
template <class T>
void write(T x)
{
    if(x < 0)
        x = -x, putchar('-');
    if(x >= 10)
        write(x / 10);
    putchar('0' + x % 10);
}
ll qsm(int a,int b,int p)
{
    ll res=1%p;
    while(b)
    {
        if(b&1)
            res=res*a%p;
        a=1ll*a*a%p;
        b>>=1;
    }
    return res;
}

int a[10];
int main()
{
   string x;
   cin>>x;
   string ans="";
   int pos=0;
   for(int i=0;i<x.size();i++)
   {
       if(x[i]=='-')cout<<'-';
       if(x[i]=='E'){
        pos=i;break;
       }
       if(isdigit(x[i]))ans.push_back(x[i]);
   }
   string tmp="";
   for(int i=pos+1;i<x.size();i++)
    {
        if(isdigit(x[i]))tmp.push_back(x[i]);
    }
    int len=stoi(tmp);
    if(len==0)
    {
        for(int i=0;i<x.size();i++)
        {
            if(x[i]=='E')break;
            if(x[i]!='+'&&x[i]!='-')cout<<x[i];
        }return 0;
    }
       if(x[pos+1]=='-')
       {
           cout<<"0.";
           for(int i=1;i<len;i++) cout<<0;
           cout<<ans;
       }
       else
       {
           if(ans.size()-1<=len)
           {
               cout<<ans;
           for(int i=0;i<len-ans.size()+1;i++)cout<<0;
           }
           else
           {
              int pos=len+1;
              for(int i=0;i<ans.size();i++)
              {
                  if(i==pos){
                    cout<<'.';
                    cout<<ans[i];
                  }
                  else cout<<ans[i];
              }
           }

       }

    return 0;
}