递归的子集和 - 我做错了什么？

Question

I am trying to solve this problem to practice thinking recursively: given a target number and an array of numbers, find out if there is a combination of the array elements that sums up to the target number. I'm new to this and I have tried everything that I can think of. Is there a problem with my logic or am I forgetting something simple? Here is my code:

function findSolution(target, arr){

  function getSum(total, num) {
    return total + num;
  }

  function find(current, push, target, i){
    current.push(push);

    if (current.reduce(getSum) === target){
      return true;
    } else if (current.length >= arr.length){
      return null;
    } else {
      return find(current, arr[i], target, i+1) || 
             find(current, 0, target, i+1);
    }

  }

return find([], 0, target, 0);

return false;
}


console.log(findSolution(23, [4, 6, 10, 1, 3] ));

The above target and array should return true (4+6+10+3) but it is returning null. Thank you very much for you help :)

Answer 1

You need to take a copy of current and you need to return the array with the values. Unfortunately, you add too much zeros to the result set.

Therefore I suggest to add a value at the place of calling the function find .

You could omit target in find , because you have already a closure over it.

 function findSolution(target, arr) { function getSum(total, num) { return total + num; } function find(current, i) { if (current.reduce(getSum, 0) === target) { // initialValue for empty arrays return current; } if (i >= arr.length) { return null; } return find(current.concat(arr[i]), i + 1) || find(current, i + 1); } return find([], 0); } console.log(findSolution(23, [4, 6, 10, 1, 3])); 

Answer 2

You need to calculate all possible combinations of the value array to find all solutions:

 function findSolution(target, arr) { const combinations = set => set.reduce( (subsets, value) => [ ...subsets, ...subsets.map(subset => [value, ...subset]) ], [ [] ] ) const getSum = (total, num) => total + num return combinations(arr).find(current => current.reduce(getSum, 0) === target ) } console.log(findSolution(23, [4, 6, 10, 1, 3]))