将字符串转成整数以及整数转成字符串

1.将字符串转换成整数

           没什么难点，就是考虑的情况比较多。

 

#include<iostream>

#include<cctype>

#include<exception>

#include<climits>

#include<cstdio>

using namespace std;



long Str2Num(const char *str)

{

     if(!str)throw new std::exception("NULL String");

     bool isNegetive = false;

     int radix = 10;

     unsigned long ret = 0;

     if(*str == '-'){

	     isNegetive = true;

	     ++str;

     }else if(*str == '+')++str;

     if(*str == '0'&&(str+1)&&*(str+1)!='x'&&*(str+1)!='0'){

	     radix = 8;

	     ++str;

     }

     else if(*str == '0'&& tolower(*(str+1))=='x'){

	     radix = 16;

	     ++str;++str;

     }

     for(;*str!='\0';++str){

	     int ch = *str;

	     if((ch - '0') <radix){

	          ret = ret*radix + ch - '0';

         }

         else if(radix == 16 && ('a'<=tolower(ch)&&tolower(ch)<='f')){

	          ret = ret*radix + tolower(ch) - 'a' + 10;

         }

         else

	          throw new exception("Invalid num");

         if(ret>LONG_MAX)throw new exception("overfolw");

     }

     return isNegetive?(-ret):ret;

}

2.将整数转换成字符串（借用别人的，感觉还是有些情况没考虑到）

char * Num2Str(int Number)



{



   char ch,*str,*right,*left;



   unsigned int Value;



   str = (char *)malloc(12*sizeof(char));



   left = right = str;



   //如果是负数，则应加上负号，left、right向后走。



   if(Number < 0)



   {



      Value = -Number;



      *str = '-';



      left++,right++;



   }



   else



      Value = (unsigned)Number;



   //把数字转换成字符串（倒置的）



   while(Value)



   {



      *right = (Value%10)+0x30;



      Value = Value/10;



      right++;



   }



   *right-- = '\0';



   //把倒置的字符串正放过来



   while(right > left)



   {



      ch = *left;



       *left++ = *right;



       *right-- = ch;



   }



   return str;



}