Java基础练习题——数组和循环练习题

1.       编写一个九九乘法法importjava.util.*;publicclass A{         public static void main(String[] args)          {                         for(int i=1;i<10;i++){//双重循环打印                          for(intj=1;j<=i;j++){                                   System.out.print(+j+"*"+i+"="+(i*j)+"\t");                          }                          System.out.println();                  }                           }} 2.       百钱买百鸡，有100元钱，要去买100只鸡，公鸡5元一只，母鸡3元一只，小鸡1元3只，问公，母，小鸡各买多少只提示： a+b+c=100  只       5a+3b+1/3c=100钱importjava.util.*;publicclass A{         public static void main(String[] args)          {                         int i=0;                  int a,b,c;                  for(a=0;a<20;a++){//a是公鸡                          for(b=0;b<34;b++){          //b是母鸡                                   c=100-a-b;                                   if(5*a+b/3.+3*c==100){//判断是否满足                                            i++;                                            System.out.printf("第%d种方法\n",i);                                            System.out.println("公鸡买"+a+"只\n"+"母鸡买"+b+"只\n"+"小鸡买"+c+"只");                                            System.out.println();                                   }                          }                  }                                                              }}   3.       有1020个西瓜，第一天卖掉总数的一半后又多卖出两个，以后每天卖剩下的一半多两个，问几天以后能卖完import java.util.*;public class A{         public static void main(String[] args)          {                         int num=1020,day=0;                  while(num>0){\\判断是否卖完                          num=num/2-2;                          day++;                  }                                    System.out.println(+day+"天以后能卖完");         }} 4.       猴子吃桃问题： 猴子第一天摘下若干个桃子，当即吃了一半，还不过瘾，又多吃了一个，第二天早上又将剩下的桃子吃了一半，又多吃一个，以后每天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。求第一天共摘了多少个？import java.util.*;public class A{         public static void main(String[] args)          {                         int num=1;                  for(int i=1;i<10;i++)//循环乘九次{         num=(num+1)*2;}                                    System.out.println("第一天共摘了"+num+"个桃子");         }} 5.       鸡兔同笼。鸡兔一共有50只，脚一共有160只，问鸡和兔各多少只?要求鸡兔至少一样一只importjava.util.*;publicclass A{         public static void main(String[] args)          {                         int a=0,b=0;                                            for(a=1;a<50;a++){//穷举出所有可能                                            {for(b=1;b<50;b++){                                                     {       if((2*a+4*b==160)&&(a+b==50))                                                              System.out.println("鸡有"+a+"只\n"+"兔有"+b+"只\n");                                                              break;                                                     }                                                                                                }                           }}   6.       有个人想知道，一年之内一对兔子能繁殖多少对？于是就筑了一道围墙把一对兔子关在里面。已知一对兔子每个月可以生一对小兔子，而一对兔子从出生后第3个月起每月生一对小兔子。假如一年内没有发生死亡现象，那么，一对兔子一年内（12个月）能繁殖成多少对？  分析：兔子的规律为数列，1，1，2，3，5，8，13，21importjava.util.*;publicclass A{         public static void main(String[] args)          {                         int sum=0;                  int i,a=1,b=1;                  for(i=3;i<=12;i++){           //后一个数等于前两个数之和                          sum=a+b;                          a=b;                          b=sum;                  }                  System.out.println("一年内能繁殖"+sum+"对");         }}  7.       求300-400之间的素数importjava.util.*;publicclass A{         public static void main(String[] args)          {                         int f=0;                  for(int i=300;i<401;i++){                          for(intj=2;j<i;j++){                                   if(i%j==0){                 //判断是否是素数                                   f=0;                                            break;                                   }else f=1;                          }                          if(f==1){                          System.out.println(i);                          }                  }                }}   8.       完成数组的排序（冒泡，插入，选择，快排，堆排均可）//  选择排序import java.util.*;public class A{         publicstatic void main(String[] args)          {                         int[]a={10,20,11,35,6,89};                  intx;                  for(inti=0;i<5;i++){//冒泡法                          for(intj=i;j<5-i;j++){                                   {if(a[j]>a[j+1]){                                            x=a[j];                                            a[j]=a[j+1];                                            a[j+1]=x;}                                   }                          }                          System.out.print(a[i]+"");                  }                  System.out.println();         }}