Finding closest sum of numbers to a given number

Question

Say I have a list [1,2,3,4,5,6,7] and I would like to find the closest sum of numbers to a given number. Sorry for the crappy explanation but here\'s an example:

Say I h

Answer 1

This proposal generates all possible combinations, collects them in an object which takes the sum as key and filters then the closest sum to the given value.

function getSum(array, sum) {
    function add(a, b) { return a + b; }

    function c(left, right) {
        var s = right.reduce(add, 0);
        if (s > sum) {
            return;
        }
        if (!result.length || s === result[0].reduce(add, 0)) {
            result.push(right);
        } else if (s > result[0].reduce(add, 0)) {
            result = [right];
        }
        left.forEach(function (a, i) {
            var x = left.slice();
            x.splice(i);
            c(left.slice(0, i), [a].concat(right));
        });
    }

    var result = [];
    c(array, [], 0);
    return result;
}

function print(o) {
    document.write('
' + JSON.stringify(o, 0, 4) + '
');
}

print(getSum([1, 2, 3, 4, 5, 6, 7], 10));
print(getSum([1, 2, 3, 4, 5, 6, 7], 14));
print(getSum([1, 2, 3, 4, 5, 6, 7], 19));