字符串和整数互转

字符串转整数

http://www.cnblogs.com/processakai/archive/2011/06/24/2089348.html

http://www.cppblog.com/prayer/archive/2010/09/06/126014.html

atoi

isspace(int x)
{
 if(x==' '||x=='\t'||x=='\n'||x=='\f'||x=='\b'||x=='\r')
  return 1;
 else  
  return 0;
}
isdigit(int x)
{
 if(x<='9'&&x>='0')         
  return 1;x` 
 else 
  return 0;

}
int atoi(const char *nptr)
{
        int c;             
        int total;        
        int sign;          

       
        while ( isspace((int)(unsigned char)*nptr) )
            ++nptr;

        c = (int)(unsigned char)*nptr++;
        sign = c;          
        if (c == '-' || c == '+')
            c = (int)(unsigned char)*nptr++;   

        total = 0;

        while (isdigit(c)) {
            total = 10 * total + (c - '0');    
            c = (int)(unsigned char)*nptr++;   
        }

        if (sign == '-')
            return -total;
        else
            return total;  
}

整数转字符串

itoa

char str[50];

sprintf(str,"%d",n);