C++ 编程/代码/标准 C 库/函数/itoa
| 语法 |
/* Convert a decimal integer to a c-style string */
char* itoa(int a, char b[]);
|
itoa 函数将一个整数参数转换为字符数组 b[]。与其他 itoa 实现相比，此函数速度不快也不简洁，但它说明了在 C++ 中使用标准库的字节级 itoa 实现。
/*
Name : itoa.cpp
Description:
Program to convert a integer to a c-style string.
Author: AM
Date : 3-4-2015
Revision and bug history:
Version : 0.1
License: GNU GPLv3
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>
*/
#include "iostream"
using namespace std;
/* Convert a decimal integer to a c-style string */
char* itoa(int a, char b[]);
/* Get number of digits in an integer */
int getNumofDecDigit(int Number);
/* get a character from digit input number */
char getStrChar(int digit);
/* Application program */
int main (void)
{
int Number =0;
char Str[10] = "";
cout << "Enter a positive or negative integer with upto 8 digits: " ;
cin >> Number;
itoa(Number, Str);
cout << "Displaying in string form: " << Str;
return 0;
}
/* Convert a decimal integer to a c-style string */
char* itoa(int a, char b[])
{
int NumofDigits = getNumofDecDigit(a);
if(a>0)
{
switch(NumofDigits)
{
case 1:
b[0]=getStrChar(a);
b[1]='\0';
break;
case 2:
b[0]= getStrChar(a/10);
b[1]= getStrChar(a%10);
b[2]='\0';
break;
case 3:
b[0]= getStrChar(a/100);
b[1]= getStrChar((a/10)%10);
b[2]= getStrChar(a%10);
b[3]='\0';
break;
case 4:
b[0]= getStrChar(a/1000);
b[1]= getStrChar((a/100)%10);
b[2]= getStrChar((a/10)%10);
b[3]= getStrChar(a%10);
b[4]='\0';
break;
case 5:
b[0]= getStrChar(a/10000);
b[1]= getStrChar((a/1000)%10);
b[2]= getStrChar((a/100)%10);
b[3]= getStrChar((a/10)%10);
b[4]= getStrChar(a%10);
b[5]='\0';
break;
case 6:
b[0]= getStrChar(a/100000);
b[1]= getStrChar((a/10000)%10);
b[2]= getStrChar((a/1000)%10);
b[3]= getStrChar((a/100)%10);
b[4]= getStrChar((a/10)%10);
b[5]= getStrChar(a%10);
b[6]='\0';
break;
case 7:
b[0]= getStrChar(a/1000000);
b[1]= getStrChar((a/100000)%10);
b[2]= getStrChar((a/10000)%10);
b[3]= getStrChar((a/1000)%10);
b[4]= getStrChar((a/100)%10);
b[5]= getStrChar((a/10)%10);
b[6]= getStrChar(a%10);
b[6]='\0';
break;
case 8:
b[0]= getStrChar(a/10000000);
b[1]= getStrChar((a/1000000)%10);
b[2]= getStrChar((a/100000)%10);
b[3]= getStrChar((a/10000)%10);
b[4]= getStrChar((a/1000)%10);
b[5]= getStrChar((a/100)%10);
b[6]= getStrChar((a/10)%10);
b[7]= getStrChar(a%10);
b[8]='\0';
break;
default:
b[0]='\0';
}
}
else
{
switch(NumofDigits)
{
case 1:
b[0]='-';
b[1]=getStrChar(a);
b[2]='\0';
break;
case 2:
b[0]='-';
b[1]= getStrChar(a/10);
b[2]= getStrChar(a%10);
b[3]='\0';
break;
case 3:
b[0]='-';
b[1]= getStrChar(a/100);
b[2]= getStrChar((a/10)%10);
b[3]= getStrChar(a%10);
b[4]='\0';
break;
case 4:
b[0]='-';
b[1]= getStrChar(a/1000);
b[2]= getStrChar((a/100)%10);
b[3]= getStrChar((a/10)%10);
b[4]= getStrChar(a%10);
b[5]='\0';
break;
case 5:
b[0]='-';
b[1]= getStrChar(a/10000);
b[2]= getStrChar((a/1000)%10);
b[3]= getStrChar((a/100)%10);
b[4]= getStrChar((a/10)%10);
b[5]= getStrChar(a%10);
b[6]='\0';
break;
case 6:
b[0]='-';
b[1]= getStrChar(a/100000);
b[2]= getStrChar((a/10000)%10);
b[3]= getStrChar((a/1000)%10);
b[4]= getStrChar((a/100)%10);
b[5]= getStrChar((a/10)%10);
b[6]= getStrChar(a%10);
b[7]='\0';
break;
case 7:
b[0]='-';
b[1]= getStrChar(a/1000000);
b[2]= getStrChar((a/100000)%10);
b[3]= getStrChar((a/10000)%10);
b[4]= getStrChar((a/1000)%10);
b[5]= getStrChar((a/100)%10);
b[6]= getStrChar((a/10)%10);
b[7]= getStrChar(a%10);
b[8]='\0';
break;
case 8:
b[0]='-';
b[1]= getStrChar(a/10000000);
b[2]= getStrChar((a/1000000)%10);
b[3]= getStrChar((a/100000)%10);
b[4]= getStrChar((a/10000)%10);
b[5]= getStrChar((a/1000)%10);
b[6]= getStrChar((a/100)%10);
b[7]= getStrChar((a/10)%10);
b[8]= getStrChar(a%10);
b[9]='\0';
break;
default:
b[0]='\0';
break;
}
}
if (a==0)
{
b[0]= '0';
b[1]='\0';
}
return b;
}
/* Get number of digits in a positive or negative integer */
int getNumofDecDigit(int Number)
{
int NumofDigits=0;
if(Number < 0)
{
Number=-Number;
}
while(Number)
{
Number/=10;
NumofDigits++;
}
return NumofDigits;
}
/* Get a character from digit input number */
char getStrChar(int digit)
{
char StrChar = ' ';
switch (digit)
{
case 0:
StrChar = '0';
break;
case 1:
case -1:
StrChar ='1';
break;
case 2:
case -2:
StrChar = '2';
break;
case 3:
case -3:
StrChar = '3';
break;
case 4:
case -4:
StrChar = '4';
break;
case 5:
case -5:
StrChar = '5';
break;
case 6:
case -6:
StrChar = '6';
break;
case 7:
case -7:
StrChar = '7';
break;
case 8:
case -8:
StrChar = '8';
break;
case 9:
case -9:
StrChar = '9';
break;
default:
StrChar ='0';
break;
}
return StrChar;
}
- 相关主题
- atoi