java - 检查简单图是否有向？

Question

任务是

"You've got a adjacency matrix (nxn). And simple graph. Print YES, if the graph is undirected and NO otherwise."

我的老师说这个程序不正确。为什么？

import java.util.Scanner;

public class Graph {

    private static Scanner scan;

    public static void main(String[] args){
        scan = new Scanner(System.in);
        final int n = scan.nextInt();

        Graph graph = new Graph();
        int[][] matrix = graph.createMatrix(n);
        boolean truth = graph.checkoriented(matrix);
        System.out.println((truth)? "Yes": "No");

        scan.close();
    }

    private boolean checkoriented(int[][] matrix) {
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix.length; j++){
                if(matrix[i][j] == 1){                  //look if  element on i pow, j column is "1";
                    boolean way = (matrix[j][i] == 1)? true: false; //if element on j pow i locumn is 1 also 
                    if(!way) return false;          // if element on j pow i locumn is 0 graph is oriented
                }
            }
        }
        return true;
    }

    private int[][] createMatrix(int n) {
        int[][] matrix = new int[n][n];
        for(int i = 0; i < n; i++){
            for(int j = 0; j < n; j++){
                matrix[i][j] = scan.nextInt();
            }
        }
        return matrix;
    }

}

Answer 1

我不知道这是否真的是一个问题，但如果你的输出应该是YES或NO，你最好打印这些而不是Yes 和 No System.out.println((truth)? "Yes": "No");。
PS:如果您的图有一条从顶点到同一个顶点的路径(我的意思是matrix[i][i] = 1)，您的算法可能会认为该图是无向的，但事实并非如此。