// ...

		n = a.length + 1;
		P = new int[n][n];
		W = new int[n][n];
		r = new int[n][n];

		// ...

		weightedPathLength = P[0][n - 1];

		root = new Node(r[0][n - 1]);
		reconstructTree(0, n - 1, root);
	}

	private void reconstructTree(int i, int j, Node parent) {
		int l = r[i][j];
		Node child;

		if (l - i - 1 > 0) {
			child = new Node(r[i][l - 1]);
			parent.left = child;

			reconstructTree(i, l - 1, child);
		}

		if (j - l > 0) {
			child = new Node(r[l][j]);
			parent.right = child;
			reconstructTree(l, j, child);
		}
	}