Pairwise

pairwise.js

function pairwise(arr, arg) {
  var usedIndexes = [];
  var usedIndexesMultiple = [];
  var indexPairs = [];
  var sum = 0;
  if (arr.length <= 1){return 0;}else{
    // find all possible pairs
    arr.reduce(function(previousValue, currentValue, currentIndex, array){
      for (var p=0;p<array.length;p++){
        if (p != currentIndex){
          if (currentValue + array[p] == arg){
              indexPairs.push([currentIndex,p]);
          }
        }
      }
    });
    // filter found pairs
    for (var k=0;k<indexPairs.length;k++){
      usedIndexes = [];
      for (var x=0;x<indexPairs.length;x++){
        if (x < indexPairs.length-1){
          filter(indexPairs, k, x);
        }else{
          usedIndexesMultiple.push(filter(indexPairs, k, x));
        }
      }
    }
    // find min sum, if there is more than one valid indexes combination
    for (var c=0;c<usedIndexesMultiple.length;c++){
      if (usedIndexesMultiple[c].length == usedIndexes.length){
        var sm1 = usedIndexesMultiple[c].reduce(function(previousValue, currentValue, currentIndex, array){return previousValue + currentValue;});
        var sm2 = usedIndexes.reduce(function(previousValue, currentValue, currentIndex, array){return previousValue + currentValue;});
        if (sm1 < sm2){
          sum = sm1;
          usedIndexes = usedIndexesMultiple[c];
        }else{
          sum = sm2;
        }
      }
    }
    //return JSON.stringify(usedIndexesMultiple);
    //return JSON.stringify(usedIndexes);
    return sum;
  }
  function filter(indexPairs, k, x){
    if (usedIndexes.length < 2){
        usedIndexes.push(indexPairs[x][0]);
        usedIndexes.push(indexPairs[x][1]);
        //sum += indexPairs[k][0] + indexPairs[k][1];
      }else{
        if (usedIndexes.indexOf(indexPairs[k][0]) == -1 && usedIndexes.indexOf(indexPairs[k][1]) == -1){
          usedIndexes.push(indexPairs[k][0]);
          usedIndexes.push(indexPairs[k][1]);
          //sum += indexPairs[k][0] + indexPairs[k][1];
        }
      }
    return usedIndexes;
  }
}
//pairwise([1,4,2,3,0,5], 7);
//pairwise([1, 3, 2, 4], 4);
pairwise([1, 1, 1], 2);
//pairwise([0, 0, 0, 0, 1, 1], 1);
//pairwise([], 100);

Pairwise.markdown

Pairwise

Function returns the sum of all indexes of elements of 'arr' that can be paired with one other element to form a sum that equals the value in the second argument 'arg'. If multiple sums are possible, function returns the smallest sum. Once an element has been used, it cannot be reused to pair with another.

A script by V.

License.