All Possible Full Binary Trees LeetCode solution in JavaScript

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var allPossibleFBT = function (n) {
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  if (n % 2 == 0) return [];
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  if (n == 1) return [new TreeNode(0)];
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  const ans = [];
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  const generate = (x) => {
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    if (x == 1) return [new TreeNode(0)];
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    const ans = [];
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    for (let l = 1; l <= x - 2; l += 2) {
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      const left = generate(l);
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      const right = generate(x - 1 - l);
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      left.forEach((l) => {
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        right.forEach((r) => {
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          const root = new TreeNode(0);
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          root.left = l;
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          root.right = r;
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          ans.push(root);
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        });
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      });
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    }
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    return ans;
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  };
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  for (let l = 1; l <= n - 2; l += 2) {
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    const left = generate(l);
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    const right = generate(n - 1 - l);
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    left.forEach((l) => {
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      right.forEach((r) => {
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        const root = new TreeNode(0);
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        root.left = l;
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        root.right = r;
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        ans.push(root);
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      });
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    });
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  }
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  return ans;
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};