Confused Student
Confused Student

Reputation: 363

Can't seem to reverse loop output correctly

So I'm trying to fill an array with the character * at certain places to get patterns. The array's size (rows and columns) are the same and is decided by user input. Has to be odd and between 3 and 11, so for example if they put in a 5 it makes a 5 by 5 array. Anyways, I'm trying to reverse the output I got from

-----------
 *        
   *       
     *    
       *  
         *
----------- to get 

 -----------
          *        
        *       
      *    
    *  
  *
 -----------  but instead I get 
 -----------
  * * * * *
  * * * * *
  * * * * *
  * * * * *
  * * * * *
 -----------   I used 5 as the size example here in case that helps

The problem is my loops don't seem to be working right, least I think. Here is the code

public static void main (String [] args) {

    int dimension = findDimension();
    char [] [] array2d = new char [dimension] [dimension];

    char star = '*';

    array2d = leftDiagonal(star, dimension);
    print(array2d);

    array2d = rightDiagonal(star, dimension);
    System.out.println();
    print(array2d);
}

public static int findDimension() {
    int dimension = 0;
    Scanner keybd = new Scanner(System.in); 
    do {
        System.out.print("Enter an odd integer between 3 and 11 please: ");
        dimension = keybd.nextInt();
    } while (dimension%2 == 0);
    return dimension;
}

public static void print(char [] [] arrayParam) {
    for (int hyphen = 0; hyphen < (arrayParam.length*2)+1; hyphen++) {
        System.out.print("-");
    }

    System.out.println();
    for(char[] row : arrayParam)
    {
        for(char c : row)
            System.out.print(" " + c);
        System.out.printf("\n");
    }

    for (int hyphen = 0; hyphen < (arrayParam.length*2)+1; hyphen++) {
        System.out.print("-");
    }
}

public static char [] [] leftDiagonal(char starParam, int dimenParam) {
    char [] [] leftD = new char [dimenParam] [dimenParam];
    for (int i = 0; i < dimenParam; i++){ 
        for (int j = 0; j < dimenParam; j++) {
            if (i == j) 
                leftD[i][j] = starParam;
            else 
                leftD[i][j] = ' ';
        }
    }
    return leftD;
}

I think the problem is specifically here though as It's what decides what's saved in the array

public static char [] [] rightDiagonal(char starParam, int dimenParam) {
    char [] [] rightD = new char [dimenParam] [dimenParam];
     for (int i = 0; i < dimenParam; i++){ 
         for (int j = 0; j < dimenParam; j++) { 
                 rightD[i][j] = ' ';
// I fill all the element spaces with blanks first then put in the *
// If there's another way to do It I'd like to know
         }
     }

    for (int i = 0; i < dimenParam; i++){ 
        for (int j = rightD.length-1; j >= 0; j--) { 
                rightD[i][j] = starParam;
        }
    }
    return rightD;
}

Upvotes: 0

Views: 81

Answers (3)

vincrichaud
vincrichaud

Reputation: 2208

Your rightDiagonal method should be similar to your leftDiagonal method. The only difference is not to check for i==j but for i==length-j

public static char [] [] rightDiagonal(char starParam, int dimenParam) {
    char [] [] rightD = new char [dimenParam] [dimenParam];
    for (int i = 0; i < dimenParam; i++){ 
        for (int j = 0; j < dimenParam; j++) {
            if (i == (dimenParam-1-j) )
                rightD[i][j] = starParam;
            else 
                rightD[i][j] = ' ';
        }
    }
    return rightD;
}

Upvotes: 1

Maximilian Horn
Maximilian Horn

Reputation: 43

From what i understood u want to split your array in the vertical mid and then mirror it on the other side:

*    |
 *   |
  *  |
   * |
    *|

to

    *|
   * |
  *  |
 *   |
*    |

So you need to divide the width of our array by 2 and then subtract the index from the * from the new width

public static void swap_array() {
int x = your_size = 4; // 4 because thats a lot easier to understad than 5
String your_array[][] = new String[x][x];

for(int i = 0; i < your_array.length; i++) {
    your_array[i][i] = "*";
}

// Now you have your start array

int new_length = your_array.length / 2; // For the mid

for(int j = 0; j < your_array.length; j++) { // Because of the 2 Dimensions
   for(int k = 0; k < your_array.length; k++) {
        if(your_array.equals("*")) {
              your_array[j][k] = your_array[j][k - new_length];
        }
        break; // Because you only got one *, so we can cut the rest then
    }
 }

 // Output

 for(int l = 0; l < your_array.length; l++) {
     for(int m = 0; m < your_array.length; m++) {
         System.out.println(your_array[l][m]);
      }
  }
}

//This hasnt been tested in IDE. Its been done from brain on the fly. Do not copy paste

Upvotes: 1

Michał Krzywański
Michał Krzywański

Reputation: 16920

Change your rightDiagonal method to

public static char [] [] rightDiagonal(char starParam, int dimenParam) {
        char [] [] rightD = new char [dimenParam] [dimenParam];

        for (int i = 0; i < dimenParam; i++){
            for (int j = 0; j < dimenParam; j++) {
                rightD[i][j] = ' ';
// I fill all the element spaces with blanks first then put in the *
// If there's another way to do It I'd like to know
            }
        }

        for (int i = 0; i < dimenParam; i++){
            for (int j = rightD.length-1; j >= 0; j--) {
                if(i + j == rightD.length - 1) {
                    rightD[i][j] = starParam;
                } else {
                    rightD[i][j] = ' ';
                }
            }
        }
        return rightD;
    }

The most important part here is condition :

if(i + j == rightD.length - 1) {
     rightD[i][j] = starParam;
}

Upvotes: 1

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