240909 트리의 순회

private static int[] postOrder;
private static int[] inOrderIndex;
private static StringBuilder result = new StringBuilder();

public static void main(String[] args) throws IOException {
	int[] inOrder;
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	int n = Integer.parseInt(br.readLine());

	inOrder = new int[n + 1];
	postOrder = new int[n + 1];
	inOrderIndex = new int[n + 1];

	StringTokenizer st = new StringTokenizer(br.readLine());
	for (int i = 1; i <= n; i++) {
		inOrder[i] = Integer.parseInt(st.nextToken());
	}

	st = new StringTokenizer(br.readLine());
	for (int i = 1; i <= n; i++) {
		postOrder[i] = Integer.parseInt(st.nextToken());
	}

	for (int i = 1; i <= n; i++) {
		inOrderIndex[inOrder[i]] = i;
	}

	constructPreOrder(1, n, 1, n);
	System.out.println(result.toString());
}

private static void constructPreOrder(int inOrderStart, int inOrderEnd, int postOrderStart, int postOrderEnd) {
	if (inOrderStart > inOrderEnd || postOrderStart > postOrderEnd) {
		return;
	}

	int root = postOrder[postOrderEnd];
	int rootIndexInOrder = inOrderIndex[root];
	result.append(root).append(" ");

	int leftTreeSize = rootIndexInOrder - inOrderStart;

	constructPreOrder(inOrderStart, rootIndexInOrder - 1, postOrderStart, postOrderStart + leftTreeSize - 1);
	constructPreOrder(rootIndexInOrder + 1, inOrderEnd, postOrderStart + leftTreeSize, postOrderEnd - 1);
}

출처:https://www.acmicpc.net/problem/2263