ค้นหาตัวเลขที่เป็นไปได้ในอาร์เรย์ที่สามารถรวมเข้ากับค่าเป้าหมายได้

function getSum(array, sum) {
    function iter(index, temp) {
        var s = temp.reduce((a, b) => a + b, 0);
        if (s === sum) result.push(temp);
        if (s >= sum || index >= array.length) return;
        iter(index, temp.concat(array[index]));
        iter(index + 1, temp);
    }

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

console.log(getSum([14, 6, 10], 40));

.as-console-wrapper { max-height: 100% !important; top: 0; }

function getSum(array, sum, limit) {
    function iter(index, temp) {
        var s = temp.reduce((a, b) => a + b, 0);
        if (s === sum) result.push(temp);
        if (s >= sum || index >= array.length || temp.length >= limit) return;
        iter(index, temp.concat(array[index]));
        iter(index + 1, temp);
    }

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

console.log(getSum([14, 6, 10], 40, 5));

.as-console-wrapper { max-height: 100% !important; top: 0; }

function getSum(array, sum) {
    function iter(index, temp) {cnt++ // counting iter calls -- remove in production code
        var s = temp.reduce((a, b) => a + b, 0);
        sum - s >= array[index]   && iter(index, temp.concat(array[index]));
        sum - s >= array[index+1] && iter(index + 1, temp);
        s === sum                 && result.push(temp);
        return;
    }

    var result = [];
    array.sort((x,y) => x-y); // this is a very cheap operation considering the size of the inpout array should be small for reasonable output.
    iter(0, []);
    return result;
}
var cnt = 0,
    arr = [14,6,10,7,3],
    tgt = 500,
    res;
console.time("combos");
res = getSum(arr,tgt);
console.timeEnd("combos");
console.log(`source numbers are ${arr}
found ${res.length} unique ways to sum up to ${tgt}
iter function has been called ${cnt} times`);

function items2T([n,...ns],t){cnt++ //remove cnt in production code
    var c = ~~(t/n);
    return ns.length ? Array(c+1).fill()
                                 .reduce((r,_,i) => r.concat(items2T(ns, t-n*i).map(s => Array(i).fill(n).concat(s))),[])
                     : t % n ? []
                             : [Array(c).fill(n)];
};

var cnt = 0, result;
console.time("combos");
result = items2T([14, 6, 10, 7, 3], 500)
console.timeEnd("combos");
console.log(`${result.length} many unique ways to sum up to 500
and ${cnt} recursive calls are performed`);

function items2T([n,...ns],t){cnt++ //remove cnt in production code
    var c = ~~(t/n);
    return ns.length ? Array(c+1).fill()
                                 .reduce((r,_,i) => r.concat(items2T(ns, t-n*i).map(s => Array(i).fill(n).concat(s))),[])
                     : t % n ? []
                             : [Array(c).fill(n)];
};

var cnt = 0, result;
console.time("combos");
result = items2T([14, 10, 7, 6, 3], 500)
console.timeEnd("combos");
console.log(`${result.length} many unique ways to sum up to 500
and ${cnt} recursive calls are performed`);