c語言問題字串轉數值

int my_atoi(char *s)
{
int i, n;

n = 0;
for (i=0; s[i] >= '0' && s[i] <= '9'; i++) {
n = 10 * n + (s[i] - '0');
}
return n;
}

int main()
{
char str[256];

printf("Please enter an positive integer: ");
scanf("%s",str);

printf("The string has been converted to an int %d\n", my_atoi(str));
}

// The function my_atoi() is what you are looking for.
// s[i] - '0' is the difference in integer between a digit with the character 0
// This function works a string from left to right. Every time the loop
// will multiple the sum by 10.