题解 | #杨辉三角的变形#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        while (scan.hasNext()) {
            int n = scan.nextInt();
            if (n == 1 || n == 2) {
                System.out.println(-1);
            }
            else if (n % 2 != 0) {
                System.out.println(2);
            }
            else {
                if (n % 4 == 0) {
                    System.out.println(3);
                }
                else System.out.println(4);
            }
            
        }
    }
}


/**
* 以下是通过 11/12的代码
*/
/*通过不了最后一个case 但是下面这个方法可以把完整的三叉杨辉三角print出来
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        while (scan.hasNext()) {
            int max = 0;
            List<Integer> list = new ArrayList<>();
            int n = scan.nextInt();
            list.add(n);
            max = Math.max(max, n);
            List<List<Integer>> res = new ArrayList<>();
            solution(max, res);
            for (int i : list) {
                getPrint(i, res);
            }
        }
    }
    public static void getPrint(int n, List<List<Integer>> res) {
        List<Integer> cur = res.get(n - 1);
        
        for (int i = 0; i < cur.size(); i++) {
            if (cur.get(i) % 2 == 0) {
                System.out.println(i + 1);
                return;
            }
        }
        System.out.println(-1);
    }
    public static void solution(int max, List<List<Integer>> res) {
        res.add(new ArrayList<>(Arrays.asList(1)));
        if (max == 1) return;
        for (int i = 2; i <= max; i++) {
            List<Integer> cur = new ArrayList<>();
            List<Integer> pre = res.get(res.size() - 1);
            int len = pre.size();
            for (int j = 0; j < len + 2; j++) {
                int number = 0;
                if (j - 2 >= 0 && j - 2 < len) number += pre.get(j - 2);
                if (j - 1 >= 0 && j - 1 < len) number += pre.get(j - 1);
                if (j >= 0 && j < len) number += pre.get(j);
                cur.add(number);
            }
            //每次添加每一行的list
            res.add(cur);
        }
    }
}
*/