1073 Scientific Notation （20 分）

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

//本題即PAT (Basic Level) Practice （中文） 1024 科學計數法 （20 分）（C++）英文版
 

//https://blog.csdn.net/m0_37454852/article/details/85858135

#include <cstdio>
#include <cstring>
#include <cmath>

int main()
{
    char str[10000] = {0};
    scanf("%s", str);//輸入
    int len = strlen(str);
    int exp = 0;
    for(int i=len -1, k = 1; str[i] != '+'; i--)//計算指數
    {
        if(str[i] == '-')
        {
            exp = -exp;
            break;
        }
        exp += (str[i] - '0')*k;
        k *= 10;
    }
    int i = 0, dot = 0;//dot為小數點所在位置
    if(str[0] == '-') printf("-");//若為負數則輸出負號，正數則無需輸出符號
    if(exp >= 0)//指數的正負小數點移動方向不同，分開考慮
    {
        for(i = 1; str[i] != 'E'; i++)
        {
            if(str[i] == '.' )
            {
                dot = i;
                continue;
            }
            if( dot && i == dot+exp+1) printf(".");//此時為小數點所在位置，列印輸出
            if(i<len)printf("%c", str[i]);
        }
        while(i<=dot+exp) printf("0"), i++;//補零
    }
    else
    {
        for(int i=0; ; i++)
        {
            if(i == 1) printf(".");//當指數為負數時，小數點必在科學計數法的整數部分之前
            if( i == -exp) break;
            printf("0");
        }
        for(i = 1; str[i] != 'E'; i++)
        {
            if(str[i] == '.' ) continue;
            printf("%c", str[i]);
        }
    }
	return 0;
}