public: int atoi(const char *str) { int n = 0,result = 0; bool positive= true; if(str==NULL) return -1; while(*(str+n)!=NULL) { if(*(str+n)>='0'&&*(str+n) <='9') { result = result*10 + *(str+n) - '0'; } else if(result!=0) { return result*(positive) -result*(!positive); } else if(*(str+...