CareerCup

#include "string.h"
#include "stdio.h"

main()
{
char str[]="ac1234e5ABCefabcd";
int slen = strlen(str);
int i;
__int64 shex=0;

//first check whether the string can be converted to INTEGER.

//convert string to integer
for(i=0; i<slen; i++)
{
if(str[i]>='0' && str[i]<='9')
{
shex = shex*16 + (str[i]-'0');
}else if(str[i]>='a' && str[i]<='f')
{
shex = shex*16 + (str[i]-'a'+10);
}else if(str[i]>='A' && str[i]<='F')
{
shex = shex*16 + (str[i]-'A'+10);
}
}

printf("%#llx\n\r", shex); //need to convert double to long

}

issues and questions:
ingore space or not? how to handle '-'?
how to print integer number which is bigger than the max value of __int64

public static int atoi(String s) {
		
		/* to check null and empty */
		if (s == null || s.length() == 0)
			return -1;
		
		int i = 0, number = 0;
		boolean neg = false, err = false;
		
		/* remove spaces from front and end */
		s = s.trim();
		
		/* check for negative sign */
		if (s.charAt(i) == '-') {
			neg = true;
			i++;
		}
		
		/* form number */
		for (; i < s.length(); i++) {

			/* check for invalid chars in between */
			if (s.charAt(i) < '0' || s.charAt(i) > '9') {
				err = true;
				System.err.println("Invalid string");
				break;
			}
			int digit = s.charAt(i) - '0';
			number = number*10 + digit;
		}
		
		if (err)
			return -1;
		
		else if (neg)
			return -number;
		
		return number;
	}

int myatoi(char* s)
{
	int a=0;
	while(*s++==' ');
	bool sign=(*s=='-')?1:0;
	if(sign) s=s+1;
	int size=strlen(s);
    for(int i=0;i<size;i++)
	{   
		if((*(s+i)<='9')&&(*(s+i)>='0'))
		{
		a=a*10+*(s+i)-'0';
		if(a>(1<<31-1)||(a<(-(1<<31))))
		{
			return 0;
		}
		}
		else
		{
			return 0;
		}
	}
	return sign?a:-a;

}

for converting String to Hex
String str="hello";
char[] chars=str.toCharArray();
StringBuffer st=new StringBuffer();
for(int i=0;i<chars.length;i++){
   st.append(Integer.toHexString((int) chars[i]));
}
System.out.println("String to hex is :+"st.toString());