杨辉三角

问题描述

打印杨辉三角

import java.util.Scanner;

public class Test5_1_1 {

	static void yanghui(int n)
	{
		int[][] a=new int[n][n];
		for (int i=0;i<n;i++)
		{
			for (int j=0;j<=i;j++)
			{
				if (j==0 || j==i)
					a[i][j]=1;
				else
					a[i][j]=a[i-1][j-1]+a[i-1][j];
			}
		}
		for (int i=0;i<n;i++)
		{
			for (int j=0;j<=i;j++)
				System.out.print(a[i][j]+"\t");
			System.out.println();
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc =new Scanner(System.in);
		System.out.println("请输入要打印多少行杨辉三角：");
		int n=sc.nextInt();
		yanghui(n);
		sc.close();
	}

}

优化后

用一维数组存储杨辉三角

import java.util.Scanner;

public class Test5_1_2 {

	static void yanghui(int n)
	{
		int[] a=new int[n+1];
		System.out.println("1");
		System.out.println("1"+"\t"+"1");
		a[1]=a[2]=1;
		for (int i=3;i<=n;i++)
		{
			a[1]=a[i]=1;
			for (int j=i-1;j>1;j--)
				a[j]=a[j]+a[j-1];
			for (int j=1;j<=i;j++)
				System.out.print(a[j]+"\t");
			System.out.println();
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc =new Scanner(System.in);
		System.out.println("请输入要打印多少行杨辉三角：");
		int n=sc.nextInt();
		yanghui(n);
		sc.close();
	}

}