public void GenEquation(ref String _equation, ref int _answer,
EquationType type)
{
int first = 0;
int second = 0;
int third = 0;
EquationMethod method1 = EquationMethod.Null;
EquationMethod method2 = EquationMethod.Null;
//decide 3 units or 4 units
if (getRandomBool())//3 units
{
get3Units(ref first, ref second, ref third, ref method1, ref method2, type);
}
else//4 units
{
get4Units(ref first, ref second, ref third, ref method1, ref method2, type);
}
_equation = first.ToString() +
Method2String(method1) + second.ToString() +
Method2String(method2) + third + " =";
_answer = doCalc(doCalc(first, second, method1), third, method2);
}
private EquationType ifCarry(int first, int second, EquationMethod method)
{
int first10 = first / 10;
int firstSingle = first % 10;
int second10 = second / 10;
int secondSingle = second % 10;
EquationType retval = EquationType.NonCarry;
if (method == EquationMethod.Add)
{
if (first10 + second10 >= 10 ||
firstSingle + secondSingle >= 10)
{
retval = EquationType.Carry;
}
}
else if (method == EquationMethod.Subtract)
{
if (first10 - second10 < 0 ||
firstSingle - secondSingle < 0)
{
retval = EquationType.Carry;
}
}
return(retval);
}
private String Method2String(EquationMethod method)
{
if (method == EquationMethod.Add)
{
return("+");
}
else if (method == EquationMethod.Subtract)
{
return("-");
}
else
{
return("null");
}
}
private int doCalc(int first, int second, EquationMethod method)
{
int retval = 0;
if (method == EquationMethod.Add)
{
retval = first + second;
}
else
{
retval = first - second;
}
return(retval);
}
private void get3Units(ref int first, ref int second, ref int third,
ref EquationMethod method1, ref EquationMethod method2,
EquationType type)
{
int carryCount = 0;
while (true)
{
carryCount = 0;
first = get1DigitNum();
second = get1DigitNum();
third = get1DigitNum();
method1 = getRandomMethod();
method2 = getRandomMethod();
if (ifCarry(first, second, method1) == EquationType.Carry)
{
carryCount++;
}
int firstAndSecond = doCalc(first, second, method1);
if (ifCarry(firstAndSecond, third, method2) == EquationType.Carry)
{
carryCount++;
}
if (type == EquationType.Carry)
{
if (carryCount == 1 && doCalc(firstAndSecond, third, method2) >= 0)
{
break;
}
}
else if (type == EquationType.NonCarry && doCalc(firstAndSecond, third, method2) >= 0)
{
if (carryCount == 0)
{
break;
}
}
}
}
private void get4Units(ref int first, ref int second, ref int third,
ref EquationMethod method1, ref EquationMethod method2,
EquationType type)
{
int carryCount = 0;
while (true)
{
method1 = getRandomMethod();
method2 = getRandomMethod();
carryCount = 0;
switch (mRandom.Next(0, 3))
{
case 0:
first = get2DigitsNum();
second = get1DigitNum();
third = get1DigitNum();
break;
case 1:
first = get1DigitNum();
second = get2DigitsNum();
third = get1DigitNum();
break;
case 2:
first = get1DigitNum();
second = get1DigitNum();
third = get2DigitsNum();
break;
}
if (ifCarry(first, second, method1) == EquationType.Carry)
{
carryCount++;
}
int firstAndSecond = doCalc(first, second, method1);
if (ifCarry(firstAndSecond, third, method2) == EquationType.Carry)
{
carryCount++;
}
if (type == EquationType.Carry && doCalc(firstAndSecond, third, method2) >= 0)
{
if (carryCount == 1)
{
break;
}
}
if (type == EquationType.NonCarry && doCalc(firstAndSecond, third, method2) >= 0)
{
if (carryCount == 0)
{
break;
}
}
}
}
