Java二维数组填充模式

Question

how can I fill two-dimensional array of given "size" to get this output:
N=1

000
010
000

N=2

0000
0110
0110
0000

N=3

00000
01110
01210
01110
00000

public static void main (String[] args) throws java.lang.Exception
{
    int x, y;
    int N = 3;
    int counter = 0;
    x = y = N + 2;
    int[][] array = new int[x][y];
    for( int i = 0; i<x; i++){
        for( int j = 0; j < y; j++){
            if( i == 0 || i == x-1 || j == 0 || j == y-1){
                array[i][j] = 0;
            } else {
                array[i][j] = 1;
            }
            System.out.print(array[i][j]);
        }
        System.out.println();
    }
}

This code gives me just 1s surrounded by 0, but I cannot figure out how to increase value to the middle of array. If N is an odd number I can use modulo, but i don't know how to do this with even numbers.

Answer 1

The value of a cell is the shortest distance to the edge of the matrix. assuming cell[i,j] , this can be either

1. i (distance from top)
2. j (distance from left)
3. Ni (distance from bottom)
4. Nj (distance from right)

so iterate over the matrix and calculate the shortest distance.

Answer 2

Here's your homework :-)

import static java.lang.Math.min;

public static void main (String[] args) throws java.lang.Exception {
    int x, y;
    int N = 5;
    int counter = 0;
    x = y = N + 2;
    int[][] array = new int[x][y];
    for (int i = 0; i < x; i++) {
        counter = 0;
        for (int j = 0; j < y; j++) {
            if (i == 0 || i == x - 1 || j == 0 || j == y - 1) {
                array[i][j] = 0;
            } else {
                array[i][j] = min(i,min(min(i,N-i+1),min(j,N-j+1)));
            }
            System.out.print(array[i][j]);
        }
        System.out.println();
    }
}

It works by using

min(i,min(min(i,N-i+1),min(j,N-j+1)))

to calculate the shortest (minimum) distance to the edge. There are 4 quadrants in the matrix with each its own calculation of distance to edge - hence the four min -operations.

N=1:

000
010
000

N=2:

0000
0110
0110
0000

N=3:

00000
01110
01210
01110
00000