嵌套矩形

import java.util.ArrayList;
import java.util.Scanner;

/**
 *嵌套矩形
 */
public class DAG01 {

	static Scanner scan = new Scanner(System.in);
	static int n, ans = 1;
	static int[] dp;
	static boolean[][] graph;
	static ArrayList<rect> list = new ArrayList<>();

	public static void main(String[] args) {
		n = scan.nextInt();
		dp = new int[n + 1];
		graph = new boolean[n + 1][n + 1];
		rect rect = new rect();
		list.add(rect);
		for (int i = 1; i <= n; i++) {
			rect = new rect();
			rect.h = scan.nextInt();
			rect.w = scan.nextInt();
			list.add(rect);
		}
		buildGraph();
		for (int i = 1; i <= n; i++) {
			int max = dfs(i);
			ans = Math.max(max, ans);
		}

		for (int i = 1; i <= n; i++) {
			if (dp[i] == ans) {
				System.out.println(ans);
				printAns(i);
				break;
			}
		}

	}

	static void buildGraph() {//建图
		for (int i = 1; i < list.size(); i++) {
			for (int j = 1; j < list.size(); j++) {
				rect mod = list.get(i);
				rect temp = list.get(j);
				if ((mod.w > temp.w && mod.h > temp.h) || (mod.w > temp.h && mod.h > temp.w)) {
					graph[i][j] = true;
				}
			}
		}
	}
	static int dfs(int i) {//记忆化搜索
		if (dp[i] > 0)
			return dp[i];
		dp[i] = 1;
		for (int j = 1; j <= n; j++) {
			if (graph[i][j]) {
				dp[i] = Math.max(dp[i], dfs(j) + 1);
			}
		}
		return dp[i];
	}
	static void printAns(int i) {//打印
		System.out.print(i);
		for (int j = 1; j <= n; j++) {
			if (graph[i][j] && dp[i] == dp[j] + 1) {
				printAns(j);
				break;
			}
		}
	}
	static class rect {
		int h;
		int w;
	}
}