#include <stdlib.h>
#include <assert.h>
int atoi(const char *str)
{
int sign = 1;
int total = 0;
assert(str!=NULL);
while(*str==' ')/*去除開頭空格*/
{
str++;
}
if(*str=='-')
{
sign = -1;
str++;
}
else if(*str=='+')
{
str++;
}
while(*str)
{
int temp = *str - '0';
assert(temp<=9&&temp>=0);
total = total*10 + temp;
str++;
}
return total*sign;
}
char *itoa(int num,char *str)
{
char *start = str;
char *temp = str;
int negative = 0;
assert(str!=NULL);
if(num<0)
{
num*=-1;
negative = 1;
}
do
{
*str = num%10 + '0',
num = num/10;
str++;
}while(num>0);
if(negative == 1)
{
*str++ = '-';
*str = '\0';
}
else
{
*str = '\0';
}
str--;
while(temp < str)
{
*temp=*temp^*str;
*str=*temp^*str;
*temp=*temp^*str;
temp++;
str--;
}
return start;
}