Java基础算法练习五题——（4）

16.输出九九乘法表

package com.myd.ex4;

public class MultiNine {

	public static void main(String[] args) {
		for (int i = 1; i <= 9; i++) {
			for (int j = 1; j <= 9; j++) {
				System.out.print(i * j + " ");
			}
			System.out.println("");
		}
	}

}

17.猴子吃桃问题：猴子第一天摘下若干个桃子，当即吃了一半，还不瘾，又多吃了一个 第二天早上又将剩下的桃子吃掉一半，又多吃了一个。以后每天早上都吃了前一天剩下的一半零一个。到第10天早上想再吃时，见只剩下一个桃子了。求第一天共摘了多少。 

package com.myd.ex4;

public class StealPeach {

	public static void main(String[] args) {
		int peach = 1;
		for (int i = 1; i < 10; i++) {
			peach = (peach + 1) * 2;
		}
		System.out.println(peach);

	}

}

18.两个乒乓球队进行比赛，各出三人。甲队为a,b,c三人，乙队为x,y,z三人。以抽签决定比赛名单。有人向队员打听比赛的名单。a说他不和x比，c说他不和x,z比，请编程序找出三队赛手的名单。

package com.myd.ex4;

public class FindPlayer {

	public static void main(String[] args) {
		int i, j, k;
		// 声明i,j,k分别为A,B,C的对手;
		for (i = 'X'; i <= 'Z'; i++) {
			for (j = 'X'; j <= 'Z'; j++) {
				for (k = 'X'; k <= 'Z'; k++) {
					if (i == 'X' || j == i || k == 'X' || k == 'Z' || k == i || k == j)
						continue;
					System.out.print("A,B,C will vs " + (char) i + "," + (char) j + "," + (char) k);
				}
			}
		}

	}

}

19.打印7行的菱形。

package com.myd.ex4;

public class PrintDiamond {

	public static void main(String[] args) {
		
		for (int i = 1; i <= 4; i++) {
			
			for (int j = 1; j <= 4 - i; j++) {System.out.print(" ");}
			
			for (int k = 1; k <= i * 2 - 1; k++) {System.out.print("*");}
			
			System.out.println();
		}
		
		for (int x = 3; x >= 1; x--)
		{
			for (int y = 1; y <= 4 - x; y++){System.out.print(" ");}
			
			for (int z = 4 - x; z <= 2 + x; z++){System.out.print("*");}
			
			System.out.println();
		}

	}

}

20.有一分数序列：2/1，3/2，5/3，8/5，13/8，21/13...求出这个数列的前20项之和。 

package com.myd.ex4;

public class SeqSum {

	public static void main(String[] args) {
		int length = 20;
		double sum = 2;
		double[] A = new double[length]; // 分子
		double[] B = new double[length]; // 分母
		A[0] = 2;
		B[0] = 1;
		for (int i = 1; i < length; i++) {
			B[i] = A[i - 1];
			A[i] = B[i - 1] + B[i];
			sum += A[i] / B[i];
		}
		System.out.println(sum);
		System.out.println(A[length - 1] + " " + B[length - 1]);
	}

}