function FindPath(root, expectNumber) {
      const result = [];
      if (root) {
        FindPathCore(root, expectNumber, [], 0, result);
      }
      return result;
    }

    function FindPathCore(node, expectNumber, stack, sum, result) {
      stack.push(node.val);
      sum += node.val;
      if (!node.left && !node.right && sum === expectNumber) {
        result.push(stack.slice(0));
      }
      if (node.left) {
        FindPathCore(node.left, expectNumber, stack, sum, result);
      }
      if (node.right) {
        FindPathCore(node.right, expectNumber, stack, sum, result);
      }
      stack.pop();
    }