Implementation of atoi function in C.

atoi C

int atoi(char *s) {
    int acum = 0;
    while((*s >= '0')&&(*s <= '9')) {
      acum = acum * 10;
      acum = acum + (*s - 48);
      s++;
    }
    return (acum);
}

//UPGRADE FOR NEGATIVE NUMBERS
int atoi(char *s) {
    int acum = 0;
    int factor = 1;
    
    if(*s == '-') {
        factor = -1;
        s++;
    }
    
    while((*s >= '0')&&(*s <= '9')) {
      acum = acum * 10;
      acum = acum + (*s - 48);
      s++;
    }
    return (factor * acum);
}