Allow to select only predifened combination from available values

Question

let us say we have parameter with A,B,C and D values. Now we want to force the user to choose only A,B,C or A,C,D or A or B or C.

Instead of Allowing all possible 16 combination, we want to allow only 5 predefined combination. I tried it but for this i have to put condition for each and every selection.

If we assume this values are bind with checkbox and we need to check whether selected values are as per our predifined combination or not.

I need to achieve this in javascript or either angular.js. Please help me with proper algorithm for such operation.

I tried below logic to achieve this but this will not infor user instantly, alert only after final submission

// multi-dimentional array of defined combinations
var preDefinedCombinations = [['a','b','c'], ['a','c','d'], ['a'], ['b'], ['c']];

// Combination user select
var selectedvalues = [];

// Function called on selection or removing value (i.e a,b,c,d)
function selectOption(value){
    var checkIndex = selectedvalues.indexof(value);
    if(checkIndex == -1){
        selectedvalues.push(value);
    }else{
        selectedvalues.splice(checkIndex, 1);
    }

}
// function called on submition of combination
function checkVaildCombination(){
    if(preDefinedCombinations.indexOf(selectedvalues) == -1){
        alert('Invalid Combination');
    }else{
        alert('Valid Combination');
    }
}

This code gives information only about combination is valid or not, not about which may be possible combinations as per selections.

Answer 1

May be following code could help you to solve ur problem

<script>
function validateForm(){
  var checkBoxValues = this.a.checked.toString() + this.b.checked.toString() + this.c.checked.toString() + this.d.checked.toString();
  if( checkBoxValues == 'truetruetruefalse'   || // abc
      checkBoxValues == 'truefalsetruetrue'   || // acd
      checkBoxValues == 'truefalsefalsefalse' || // a
      checkBoxValues == 'falsetruefalsefalse' || // b
      checkBoxValues == 'falsefalsetruefalse' ){ // c
    return true;
  }
  return false;
}
</script>
  <form onsubmit="return validateForm()" action="javascript:alert('valid')">
    <input type="checkbox" name="mygroup" id="a">
    <input type="checkbox" name="mygroup" id="b">
    <input type="checkbox" name="mygroup" id="c">
    <input type="checkbox" name="mygroup" id="d">
    <input type="submit">
  </form>

Answer 2

stolen from https://stackoverflow.com/a/1885660/1029988 :

function intersect_safe(a, b)
{
  var ai=0, bi=0;
  var result = new Array();

  while( ai < a.length && bi < b.length )
  {
     if      (a[ai] < b[bi] ){ ai++; }
     else if (a[ai] > b[bi] ){ bi++; }
     else /* they're equal */
     {
       result.push(a[ai]);
       ai++;
       bi++;
     }
  }

  return result;
}

then in your code:

function checkVaildCombination(){
    function get_diff(superset, subset) {
        var diff = [];
        for (var j = 0; j < superset.length; j++) {
            if (subset.indexOf(superset[j]) == -1) { // actual missing bit
                diff.push(superset[j]);
            }
        }
        return diff;
    }

    if(preDefinedCombinations.indexOf(selectedvalues) == -1){
        missing_bits = [];
        diffed_bits = [];
        for (var i = 0; i < preDefinedCombinations.length; i++) {
            var intersection = intersect_safe(preDefinedCombinations[i], selectedvalues);
            if (intersection.length == selectedvalues.length) { // candidate for valid answer
                missing_bits.push(get_diff(preDefinedCombinations[i], intersection));
            } else {
                var excess_bits = get_diff(selectedvalues, intersection),
                    missing_bit = get_diff(preDefinedCombinations[i], intersection);

                diffed_bits.push({
                    excess: excess_bits,
                    missing: missing_bit
                });
            }
        }

        var message = 'Invalid Combination, if you select any of these you`ll get a valid combination:\n\n' + missing_bits.toString();
        message += '\n\n Alternatively, you can reach a valid combination by deselected some bits and select others:\n';

        for (var j = 0; j < diffed_bits.length; j++) {
            message += '\ndeselect: ' + diffed_bits[j].excess.toString() + ', select: ' + diffed_bits[j].missing.toString();
        }
        alert(message);
    } else {
        alert('Valid Combination');
    }
}

you will of course want to format the output string, but that code will (hopefully, it is napkin code after all) give you the missing bits to make valid combos with what you've got selected already