Pat(A) 1073. Scientific Notation (20)

原题目：

原题链接：https://www.patest.cn/contests/pat-a-practise/1073

1073. Scientific Notation (20)

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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 file 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

题目大意

给出一个数的科学计数法表示形式，写出起普通形式，保留精确度，包括0。

解题报告

分析它的小数点向左移动还是向右移动，根据E后面的数值区分，如果小于0，前面加前导0和“.”后面直接连起来就行，如果大于0，分析数字应该有的长度及小数点的位置讨论。

注意事项：

1. 数位较长，采用计算的方法不可取。
2. 分析好小数点的位置。

代码

#include "iostream"#include "string"using namespace std;int main(){    string s;    int pose;    cin>>s;    if (s[0] == '-'){        cout<<'-';    }    int l = s.length();    int e = s.find('E');    pose = stoi(string(s,e + 1,l));    if(pose < 0){        cout<<"0.";        for(int i=1;i<= -pose - 1;i++)            cout<<0;        for(int i = 1;i < e; i++)            if(s[i] !=  '.')                cout<<s[i];        cout<<endl;    }else{        int point = pose + 2;        int len = max(e-2,point-1);        //cout<<len<<endl;        for(int i = 1; i <= len; i++){            if(i<e && s[i] == '.'){                point ++;                len ++;                continue;            }            if(i == point)                cout<<'.';            if(i < e)                cout<<s[i];            else                cout<<0;        }        cout<<endl;    }    //system("pause");}