250308 굉장한 학생

static class SegmentTree {
	private final int[] tree;
	private final int size;

	public SegmentTree(int n) {
		size = n;
		tree = new int[2 * size];
		Arrays.fill(tree, Integer.MAX_VALUE);
	}

	public void update(int index, int value) {
		index += size - 1;
		tree[index] = value;

		while (index > 1) {
			index /= 2;
			tree[index] = Math.min(tree[2 * index], tree[2 * index + 1]);
		}
	}

	public int query(int left, int right) {
		left += size - 1;
		right += size - 1;
		int minValue = Integer.MAX_VALUE;

		while (left <= right) {
			if (left % 2 == 1)
				minValue = Math.min(minValue, tree[left++]);
			if (right % 2 == 0)
				minValue = Math.min(minValue, tree[right--]);
			left /= 2;
			right /= 2;
		}

		return minValue;
	}
}

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

	int n = Integer.parseInt(br.readLine());
	int[] firstRank = new int[n + 1];
	int[] secondRank = new int[n + 1];

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

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

	int result = processRanks(br, n, firstRank, secondRank);

	bw.write(Integer.toString(result));
	bw.flush();
	bw.close();
}

private static int processRanks(BufferedReader br, int n, int[] firstRank, int[] secondRank) throws IOException {
	int segmentTreeSize = initializeSegmentTreeSize(n);
	SegmentTree segmentTree = new SegmentTree(segmentTreeSize);

	int result = 0;
	StringTokenizer st = new StringTokenizer(br.readLine());
	for (int i = 0; i < n; i++) {
		int value = Integer.parseInt(st.nextToken());
		int index = secondRank[value];

		if (segmentTree.query(1, index - 1) > firstRank[value]) {
			result++;
		}
		segmentTree.update(index, firstRank[value]);
	}
	return result;
}

private static int initializeSegmentTreeSize(int n) {
	int size = 1;
	while (size < n) {
		size *= 2;
	}
	return size;
}

출처:https://www.acmicpc.net/problem/2336