Controlling values in boolean array

Question

bool[] isAvailable = new boolean[5];

Initially im setting all values in the array to true.

I'm now changing (one at a time) the values (randomly chosen) to false and I need a way to turn one of the false values back to true if there exists more than 3 false values. Furthermore it must not be the last changed value that becomes true.

I'm using LinQ and C#:

void checkArray() {
    if (isAvailable.Where (c => !c).Count () > 3) {
        int posOpen = ???;
    }
}

Scenario:

[true,true,true,true,true] -> [true,true,true,true,false] -> 

[true,true,false,true,false] -> [false,true,false,true,false] -> 

[false,true,true,true,false] -> [false,false,true,true,false] etc..

Can anyone explain how-to?

Does the index of the value changed back to true have to be randomly selected, or can it just be the value which has been false longest? — StriplingWarrior
– StriplingWarrior, Commented Apr 17, 2015 at 19:46
If you just want to find all indices whose value is false, do var falseIndices = Enumerable.Range(0, isAvailable.Length).Select(i => !isAvailable[i]);. — dbc
– dbc, Commented Apr 17, 2015 at 19:47
But there's nothing in the code you've shown that indicates which has been false longest. — dbc
– dbc, Commented Apr 17, 2015 at 19:47

StriplingWarrior · Accepted Answer · 2015-04-17 19:59:38Z

4

Rather than changing the index values directly, you would do well to wrap the changes in a helper method, which can then respond to changes. You can keep track of the order in which items were made false using a Queue, and then change them back once the Queue hits a certain size.

void Main()
{
    ShowArray();        //[True, True, True, True, True]
    ChangeValue(1);
    ShowArray();        //[True, False, True, True, True]
    ChangeValue(4);
    ShowArray();        //[True, False, True, True, False]
    ChangeValue(3);
    ShowArray();        //[True, False, True, False, False]
    ChangeValue(0);
    ShowArray();        //[False, True, True, False, False]
}

bool[] _array = {true,true,true,true,true};
Queue<int> _changed = new Queue<int>();
void ChangeValue(int index)
{
    if(_array[index]) // do nothing if it was already false
    {
        _array[index] = false;
        _changed.Enqueue(index);
        if(_changed.Count() > 3)
        {
            _array[_changed.Dequeue()] = true;
        }
    }
}

void ShowArray()
{
    Console.WriteLine("[" + string.Join(", ", _array) + "]");
}

edited Apr 17, 2015 at 19:59

answered Apr 17, 2015 at 19:54

StriplingWarrior

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1 Comment

Anonymous Over a year ago

Haven't used Queue before. So thanks alot for showing me and it worked perfectly

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