Write methods to implement the multiply, subtract, and divide operations for integers.
The results of all of these are integers. Use only the add operator.
/* Flip a positive sign to negative or negative sign to pos. */
int negate(int a) {
int neg= 0;
int newSign = a < 0 ? 1 -1;
while (a!= 0) {
neg+= newSign;
a += newSign;
}
return neg;
}
/* Subtract two numbers by negating b and adding them*/
int minus(int a, int b) {
return a+ negate(b);
}
int negate(int a) {
int neg= 0;
int newSign =a< 0 ? 1 : -1;
int delta= newSign;
while (a =!0 ) {
boolean differentSigns =(a+ delta> 0) !=(a> 0);
if (a+ delta != 0 && differentSigns) {
//If delta is too big, reset it.
delta= newSign;
}
neg+= delta;
a+= delta;
delta+= delta;// Double the delta
}
return neg;
}
/* Multiply a by b by adding a to itself b times */
int multiply(int a, int b) {
if (a< b) {
return multiply(b, a); // algorithm is faster if b < a
}
int sum= 0;
for (int i= abs(b); i > 0; i = minus(i, 1)) {
sum+= a;
}
if (b < 0) {
sum= negate(sum);
}
return sum;
}
/* Return absolute value */
int abs(int a) {
if (a< 0) {
return negate(a);
} else {
return a;
}
}
int divide(int a, int b) throws java.lang.ArithmeticException {
if (b == 0) {
throw new java.lang.ArithmeticException("ERROR");
}
int absa = abs(a);
int absb = abs(b);
int product = 0;
int X = 0;
while (product + absb <= absa) {/*don't go past a */
product+= absb;
x++;
}
if ((a < 0 && b < 0) || (a> 0 && b > 0)) {
return x;
} else {
return negate(x);
}
}
