I was working on Combination Sum exercise and there is something that i wanted to do and i dont know if it’s possible and how to do it

1. How to add memoization ?

2. If memoization is not possible can i use child process to distribute the calculation and make it faster or is there another way ?

here is the code:

function countChange(money, coins) {
  const result = [];
  const memo = {};
  function recurse(start, leftOver, selection) {
    if (leftOver < 0) return;
    if (leftOver === 0) {
      result.push(selection);
      return selection;
    }

    for (var i = start; i < coins.length; i++) {
      recurse(i, leftOver - coins[i], selection.concat(coins[i]));
    }
  }
  recurse(0, money, []);
  console.log(result);
  return result.length;
}

const long_result = countChange(999, [1, 2, 5, 10, 20, 50, 100]);
// const long_result = countChange(4, [1, 2]);
console.log(long_result);

I tried adding memoization but the results were not correct maybe i did not implemented it in the right way here is the code:

function countChange(money, coins) {
  const result = [];
  const memo = {};
  function recurse(start, leftOver, selection) {
    if (leftOver in memo) return memo[leftOver];
    if (leftOver < 0) return;
    if (leftOver === 0) {
      result.push(selection);
      // memo[leftOver] = selection;
      return selection;
    }

    for (var i = start; i < coins.length; i++) {
      memo[leftOver] = recurse(i, leftOver - coins[i], selection.concat(coins[i]));
    }
  }
  recurse(0, money, []);
  console.log(result);
  return result.length;
}

// const long_result = countChange(999, [1, 2, 5, 10, 20, 50, 100]);
const long_result = countChange(4, [1, 2]);
console.log(long_result);