Java uses a two-dimensional array to print Yang Hui's triangle

Purpose:

Use a two-dimensional array to print a 10-line Yang Hui triangle.

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Idea:

1. There is 1 element in the first row, and the nth row There are n elements;

2. The first element and the last element of each row are both 1;

3. Starting from the third row, for the non-first element and the last An element of an element. That is: yanghui[i][j] = yanghui[i-1][j-1] yanghui[i-1][j];

This is the array sum For the combination of nested loops, follow the prompts step by step, and the effect is as shown in the picture above.

Code implementation:

package com.atguigu.exer;

import java.util.concurrent.ForkJoinPool;

public class ArrayDemo {
    public static void main(String[] args) {
        //1.二维数组的动态初始化
        int[][] yangHui = new int[10][];

        //2.二维数组的外层元素的动态初始化
        for(int i = 0;i < yangHui.length;i++){
            yangHui[i] = new int[i + 1];
        }

        //3. 给二维数组的内层元素赋值
        for(int i = 0;i < yangHui.length;i++){
            //3.1 每一行的首末元素赋值为1
            yangHui[i][0] = yangHui[i][i] = 1;
            //3.2 每一行的非首末元素赋值。规律为：yanghui[i][j] = yanghui[i-1][j-1] + yanghui[i-1][j];
            //if(i >= 2){
                for(int j = 1;j < yangHui[i].length - 1;j++){
                    yangHui[i][j] = yangHui[i-1][j-1] + yangHui[i-1][j];
                }
            //}

        }

        //4. 遍历二维数组
        for (int i = 0; i < yangHui.length; i++) {
            for (int j = 0; j < yangHui[i].length; j++) {
                System.out.print(yangHui[i][j] + "  ");
            }
            System.out.println();
        }
    }
}

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