CareerCup

int atoi(char* str)
{
int ret=0, i=0, flag=0;
if(str == NULL)
return -1;

if(str[0] == '-')
{
flag = 1;
i++;
}

while(str[i] != '\0')
{
if(!(str[i]>=48 && str[i]<=57))
return -1;

ret = ret * 10 + ((int)str[i] - '0');
i++;
}

return !flag ? ret : ret*-1;
}

/* Create your own atoi() function */ 
#include <stdio.h>
#include <string.h>

int myatoi(char* buf); 

int main()
{
	char buf[20] = {0}; 
	printf("Enter a number: ");
	scanf("%s",buf); 
	
	int i = myatoi(buf); 	
	printf("myatoi() returned [%d]\n", i); 
	return 0; 
}
	
int myatoi(char* buf)
{
	int sum = 0; 
	int mult = 1; 
	int currVal = 0;
	
	int nCount = strlen(buf); 
	for( int i = nCount-1; i >= 0; i-- )
	{
		if( i == 0 && buf[i] == '-' )
		{
			sum *= -1; 
		}
		else
		{
			currVal = buf[i] - '0'; 
			currVal *= mult; 
			sum += currVal; 
			mult *= 10; 
		}
	}
	return sum; 
}

atoi(char *s){
int no=0;
int i=0;
while(*(s+i)){
no=no<<3+no<<1+*(s+i);
i++;
}

logic:=take first no of string and shift by 10 (8+2)

- Invalid character
- Overflow exception
- Positive and Negative numbers.

int MyAtoi(char *inputParam){
if(*inputParam == 0) throw new FormatException();

int result = 0;

bool isNegative = false;
if(*inputParam == '-'){
inputParam++;
isNegative = true;
}
if(*inputParam == 0) throw new FormatException();
while(*inputParam){
if(*inputParam >= 0x32 && *inputParam < 0x3C){
int tempResult = (result
+ (*inputParam - 0x32)
)
* ((*(inputParam + 1) == 0) ? 1 : 10);
if(tempResult < result) throw new OverflowException();
result = tempResult;

} else {
throw new FormatException();
}
}
return result;

}

- Invalid character
- Overflow exception
- Positive and Negative numbers.

int MyAtoi(char *inputParam){
  if(*inputParam == 0) throw new FormatException();
  int result = 0;
  bool isNegative = false;
  if(*inputParam == '-'){
      inputParam++;
      isNegative = true;
  }
  if(*inputParam == 0)  throw new FormatException();
  while(*inputParam){
     if(*inputParam >= 0x32 && *inputParam < 0x3C){
        int tempResult = (result
                    + (*inputParam - 0x32) 
                 )
                 * ((*(inputParam + 1) == 0) ? 1 : 10);
        if(tempResult < result) throw new OverflowException();
        result = tempResult;
     } else {
       throw new FormatException();
     }
  }
return result * (isNegative ? -1:1); 
}

int rec_atoi(char *str,int *n){
        int mul = 1;
        if( *str != '-' &&(str == NULL || *str>'9' || *str <'0')){
                *n = 0;
                return 1;
        }
        else if( *str <='9' && *str >='0'){
                mul = rec_atoi(str+1,n);
                *n += (*str-'0')*mul;
                return mul*10;
        }
        else if(*str == '-'){
                mul = rec_atoi(str+1,n);
                *n = *n*(-1);
                return 1;
        }
}
void main(){
        int n = 0;
        rec_atoi("110352a2a",&n);
        printf(" %d \n ",n);
}