题解 | 小红的排列构造①

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
     public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        StreamTokenizer in = new StreamTokenizer(br);

        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));

        in.nextToken();
        int n = (int) in.nval;

        int[] arr = new int[n];

        if(n<=2){
            out.println(-1);
        }else{
            arr[0]=3;// 第一个元素固定为3
            for (int i = 1; i < n; i++) {
                arr[i]=i+1;//从第2个元素开始，值为「索引+1」
            }
            arr[2]=1;// 第三个元素强制改为1

            for(int i=0;i<n;i++){
                out.print(arr[i]+(i == n - 1 ? "" : " "));
            }
        }



        out.flush();
        out.close();
        br.close();
    }
}