2D Array Yang Hui Triangle

In the two-dimensional array learning of java basic grammar, we will come into contact with Yang Hui's triangle. Let's take a look at the realization process of Yang Hui's triangle.

/*
1
1 1
1 2 1
1 3 3  1
1 4 6  4  1
1 5 10 10 5 1
规律
1.第一行有1个元素，第n行有n行元素
2.每一行的第一个元素和最后一个元素都是1
3.从第三行开始，对于非第一个元素和最后一个元素的元素的值 arr[i][j]
  arr[i][j] = arr[i-1][j] + arr[i-1][j-1]
*/
public class yanghui {
    public static void main(String[] args) {
        int[][] arr = new int[10][];
        //遍历arr的每一个元素
        for (int i = 0; i < arr.length; i++) {
            //给每个一维数组开空间
            arr[i] = new int[i + 1];
            //遍历给每个一维数组赋值
            for (int j = 0; j < arr[i].length; j++) {
                //对应规律2
                if(j == 0 || j == arr[i].length - 1){
                    arr[i][j] = 1;
                }else {
                    //对应规律3
                    arr[i][j] = arr[i-1][j] + arr[i-1][j-1];
                }                 
            }
        }

        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) {
                System.out.print(arr[i][j] + " ");    
            }
            System.out.println();
        }

    }
}

The 10-row Yang Hui triangle is as follows: