Connectivity Problem

MainClass.java

public class MainClass {
   public static void main(String args[]){

       String sampleData = "1-2,2-3,3-4,9-0,0-9,2-4,5-6,9-0,8-9,9-8,1-9,1-3,1-10,10-13,11-12,12-15,15-19,19-22,20-22,21-20,18-20,1-20,1-19,1-9,20-21,21-22,22-0,1-22,9-20,9-23,19-8,2-18,7-21,2-21,21-3";
//       String sampleData2 = "3-4,4-9,8-0,2-3,5-6,2-9,5-9,7-3,4-8,5-6,0-2,6-1,6-1,0-2,5-6,4-8,7-3,5-9,2-9,5-6,2-3,8-0,4-9,3-4";
//       String sampleData3 = "3-4,4-9,8-0,2-3,5-6,2-9,5-9,7-3,4-8,5-6,0-2,6-1,3-4,4-9,8-0,2-3,5-6,0-2,5-9,7-3,4-8,5-6,2-9,6-1,3-4,4-9,8-0,2-3,5-6,2-9,5-9,7-3,4-8,5-6,0-2,6-1";

       ProblemMatrix matrix = new ProblemMatrix(new boolean[50][50]);
       matrix.setUpMatrix();

       String[] pairs = sampleData.split(",");
       for(String pair : pairs){
           String[] pairSplit = pair.split("-");
           int rowNumber = Integer.parseInt(pairSplit[0]);
           int columnNumber = Integer.parseInt(pairSplit[1]);
           matrix.checkConnectivity(rowNumber,columnNumber);
       }

   }
}

ProblemMatrix.java

public class ProblemMatrix {

    private boolean[][] matrix;
    private int lastVisited; //to avoid infinite loops

    public ProblemMatrix(boolean [][] matrix){
        this.matrix = matrix;
    }

    public boolean[][] getMatrix(){
         return this.matrix;
    }

    public void updateMatrix(int row, int column, boolean tf){
        this.matrix[row][column] =  tf;
    }

    public void setUpMatrix(){
        for (int i = 0; i < this.matrix.length; i++) {
            for (int j = 0; j < this.matrix[0].length; j++) {
                if (i == j) {   //for similar indexes
                    matrix[i][j] = true;
                } else {
                    matrix[i][j] = false;
                }
            }
        }
    }

    public void checkConnectivity(int row, int column){
       if(this.matrix[row][column] && this.matrix[column][row]){
           System.out.print("--" + " ");
       }else{
           if(checkTransitivity(row, column)){
               System.out.print("--" + " ");
           }else{
               updateMatrix(row,column,true);
               updateMatrix(column,row,true);
               System.out.print(row + "-" + column + " ");
           }
           lastVisited = row;
       }
    }

    private boolean checkTransitivity(int row, int column){
//       if(row == 1 && column == 19) System.out.println("start - "+lastVisited);
//       if(column == 19) System.out.println(row + " " + lastVisited);
      //base case
       if(this.matrix[row][column]){
           return true;
       }else{
         //go over the row
         for(int i = 0; i < this.matrix[row].length; i++){
           if(this.matrix[row][i] && i != row && i != lastVisited){
                lastVisited = row;
                return checkTransitivity(i, column);  //column is your target
           }
         }
       }
       return false;
    }
}

The commented sample data in MainClass work fine, except for the one being used.

The problem occurs when a visited node no longer has neighbors and returns false.