PAT A1073 Scientific Notation （20 分）—

PAT A1073 Scientific Notation （20 分）——字符串转数字

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

Input Specification:

Each input contains one test case. For each case, there is one line containing the real number

Output Specification:

For each test case, print in one line the input number

Sample Input 1:

+1.23400E-03

Sample Output 1:

0.00123400

Sample Input 2:

-1.2E+10

Sample Output 2:

-12000000000

 1 #include <stdio.h>
 2 #include <map>
 3 #include <algorithm>
 4 #include <iostream>
 5 #include <string>
 6 #include <math.h>
 7 using namespace std;
 8 
 9 int main(){
10     string a;
11     cin >> a;
12     if (a[0] == '-'){
13         printf("-");
14         a.erase(0, 1);
15     }
16     else if (a[0] == '+'){
17         a.erase(0, 1);
18     }
19     a.erase(1, 1);
20     int pos_e;
21     pos_e = a.find('E');
22     string sub_str = a.substr(pos_e + 1, a.length() - pos_e - 1);
23     int flag = 1;
24     if (sub_str[0] == '-')flag = -1;
25     a.erase(pos_e, 1 + sub_str.length());
26     sub_str.erase(0, 1);
27     while (!sub_str.empty() && sub_str[0] == '0'){
28         sub_str.erase(0, 1);
29     }
30     int exp = 0;
31     if (sub_str.empty())exp = 0;
32     else{
33         for (int i = 0; i < sub_str.length(); i++){
34             exp = exp * 10 + sub_str[i] - '0';
35         }
36     }
37     int extra = 0;
38     if (flag == -1){
39         for (int i = 0; i < exp - 1; i++){
40             a.insert(0, "0");
41         }
42         a.insert(0,"0.");
43     }
44     else{
45         int l = a.length();
46         
47         if (exp >= l - 1){
48             for (int i = 0; i < exp - l+1;i++){
49                 a.insert(a.length(),"0");
50             }
51             
52         }
53         else{
54             a.insert(1 + exp, ".");
55         }
56     }
57     cout << a;
58     system("pause");
59 }

View Code

注意点：和B1024一样，就是分情况实现，字符串转数字，要记得字符串的find，erase，substr操作。

---------------- 坚持每天学习一点点