C++ string转换成int

C++ string转换成int

 

 1 #include <iostream>
 2 #include <cstdlib>
 3 #include <cctype>//isspace()
 4 #include <climits>//INT_MAX INT_MIN
 5 #include <string>
 6 using namespace std;
 7 
 8 /*打印错误输出*/
 9 void PrintError (std::string error);
10 /*string转换成int*/
11 int StrToInt (const char *s);
12 
13 void PrintError (std::string error)
14 {
15     std::cout << error <<", please input a right string" << std::endl;
16     exit (EXIT_FAILURE);
17 }
18 
19 int StrToInt (const char *s)
20 {
21     //处理输入为NULL
22     if (NULL == s)
23     {
24         PrintError ("string is NULL");
25     }
26 
27     //忽略前面的空白符
28     while (isspace (*s))
29     {
30         ++s;
31     }
32 
33     //处理输入为负数或者带+的整数的情况
34     bool negFlag = false;
35     if ('-' == *s)
36     {
37         negFlag = true;
38         ++s;
39     }
40     else if ('+' == *s)
41     {
42         ++s;
43     }
44 
45     //进行转换
46     long long result = 0;
47     long long temp = 0;
48     while ('\0' != *s)
49     {
50         //判断是否有小数点
51         if ('.' == *s)
52         {
53             break;
54         }
55         temp = *s - '0';
56         if (0 > temp ||
57                 9 < temp)
58         {
59             PrintError ("string is wrong");
60         }
61         result = result * 10 + temp;
62         if ((false == negFlag && INT_MAX < result) ||
63                 (true == negFlag && (INT_MIN > 0 - result)))//溢出
64         {
65             PrintError ("Overflowed");
66             exit (EXIT_FAILURE);
67         }
68         ++s;
69     }
70     if ( true == negFlag)
71     {
72         result = 0 - result;
73     }
74     return result;
75 }
76 
77 int main ()
78 {
79     string s = "3333333.23";
80     cout << StrToInt (s.c_str ()) << endl;
81     s = "  +123";
82     cout << StrToInt (s.c_str ()) << endl;
83     s = "  -123.23";
84     cout << StrToInt (s.c_str ()) << endl;
85     s = "  1234235353463465465467";
86     cout << StrToInt (s.c_str ()) << endl;
87     return 0;
88 }

 

运行结果如下：

3333333
123
-123
Overflowed, please input a right string

 

posted on 2017-03-02 21:29  uestcjoel  阅读(249)  评论(0)    收藏  举报

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