面试中的一些算法问题

要求从键盘输入10个数并按从小到大的顺序排序。用JAVA做。

public static void main(String args[]){

              /*int [] num={1,2,5,4,3,6};

              Arrays.sort(num);

              for(int i=0;i<num.length;i++)

                     System.out.println(num[i]);*/

              int[] sz=new int[10];

              int n=0;

              String str;

              InputStreamReader isr=new InputStreamReader(System.in);

              BufferedReader br=new BufferedReader(isr);

              try{

              while(n<10)

              {

              str=br.readLine();

              sz[n]=Integer.parseInt(str);

              n++;

              }

              Arrays.sort(sz);

              //sort(sz,10);

              for(int i=0;i<10;i++)

              System.out.println(sz[i]);

              }

              catch(Exception e){}

              }

       private static void sort(int[] sz,int n) {

                     int temp,i,j;

                     for(i=n-1;i>0;i--)

                     for(j=0;j<i;j++)

                     if(sz[j]>sz[j+1])

                     {

                     temp=sz[j];

                     sz[j]=sz[j+1];

                     sz[j+1]=temp;

                     }

              }

 

1.父子俩的年龄：父亲今年30岁，儿子今年6岁，问多少年后父亲的年龄是儿子年龄的2倍。*/

package exec;.

public class Age ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        int father = 30;

        int son = 6;

        for(int i=1;i<100;i++)

        ...{

            if((father+i)==((son+i)*2))...{

                System.out.println(i + " 年");} } }}

2.编写程序,将两个各有6个整数的数组,合并成一个由小到大排列的数组,(该数组的长度为12)*/

package exec;

import java.util.Arrays;

public class Arrary ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        int a[] = ...{ 1, 3, 5, 8, 9, 4 };

        int b[] = ...{ 2, 4, 7, 6, 5, 9 };

        int c[] = new int[12];

        for (int i = 0; i < 6; i++) ...{

            c[i] = a[i];

            c[i + 6] = b[i];

        }

        Arrays.sort(c);

        for (int i = 0; i < 12; i++) ...{

            System.out.print(c[i] + " ");   } }}

3.一个球从100米高度自由落下后，反弹回原来高度的一半。按此规律，到第10次落地时，行程共有多少米？ * 然后将反弹起多高？ */

package exec;

public class BallFall ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        float heigher = 100;

        float sum = 0;

        for (int i = 1; i < 10; i++) ...{

            heigher /= 2;

            sum += heigher;

            System.out.println("第" + i + "次" + "总行程" + sum + "米" + "反弹"

                    + heigher + "米"); } }}

4. 换硬币：把一元人民币换成5分、2分、1分的硬币，有多少种换法? */

package exec;

public class ChangeCoin ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        int num = 0;

        for (int i = 1; i <= 20; i++) ...{

            for (int j = 1; j <= 50; j++) ...{

                for (int k = 1; k <= 100; k++) ...{

                    if (5 * i + 2 * j + 1 * k == 100) ...{

                        num += 1;     }   }          }        }

        System.out.print(num + "种换法");   }}

5.牛的繁殖问题 ：有位科学家曾出了这样一道数学题：有一头母牛，它每年年初要生一头小母牛；

* 每头小母牛从第四个年头起，每年年初也要生一头小母牛。按此规律，若无牛死亡，第20年头上共有多少头母牛？*/

package exec;

public class CountCow ...{

    int[] cowNumber = new int[21];

    public void count(int increaseCycle, int years) ...{

        cowNumber[0] = 1;

        for (int currentYear = 1; currentYear <= years; currentYear++) ...{

            if (currentYear < increaseCycle) ...{

                cowNumber[currentYear] = cowNumber[currentYear - 1] + 1;

            } else ...{

                cowNumber[currentYear] = cowNumber[currentYear - 1]

                        + cowNumber[currentYear - increaseCycle + 1];

            }

            System.out.println("第" + currentYear + "年" + cowNumber[currentYear]);    } }

    public static void main(String[] args) ...{

        int increaseCycle = 4;

        int years = 20;

        CountCow cow = new CountCow();

        cow.count(increaseCycle, years);   }}

6.打印出500之内所有能被7或9整除的数*/

package exec;

public class Divide ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        for (int i = 0; i <= 500; i++) ...{

            if ((i % 7 == 0) | (i % 9 == 0)) ...{

                System.out.print(i + " "); }   } }}

7. * 编写一个Java程序 使它随即产生1800到2000之间的年份,打印它是否是一个闰年,闰年是1584年以后的年份,它要能被400整除, * 要能被4整除但是不能被100整除,已知使用Math.random()方法可以产生0到1之间的随即小数. ) */

package exec;

public class EmergerYear ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        for (int i = 0; i < 100; i++) ...{

            long year = (Math.round(Math.random() * 200) + 1800);

            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) ...{

                System.out.println(year + "是闰年!");

            } else             System.out.println(year + "不是闰年!");   } }}

8.编写程序以递归的方式实现1+2+3+...+n(n=200)的计算.*/

package exec;

public class Number ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        System.out.print(numbers(200));

    } public static int numbers(int n)...{

        return n<=1?1:n+numbers(n-1);    }}

9.给定一个数,并由键盘输入若干个数,找出与预先给定的数最接近的数,并指出它是由键盘输入的第几个数。

package exec;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

public class NumberCompare ...{

    public static final int NUMBER = 80; // 给定一个要比较的数

    public static void main(String args[]) ...{

        System.out.print("Please input numbers: ");

        BufferedReader io = new BufferedReader(new InputStreamReader(System.in));

        try ...{

            // 从键盘输入若干数

            String line = io.readLine();

            // 放入数组中

            String[] items = line.split(" ");

            int temp = 5000, x = 0, place = 0;

            System.out.println("target number: 80");

            // 和给定的数比较大小

            for (int i = 0; i < items.length; i++) ...{

                if (Integer.parseInt(items[i]) > NUMBER) ...{

                    x = Integer.parseInt(items[i]) - NUMBER;

                } else ...{

                    x = NUMBER - Integer.parseInt(items[i]);

                }

                if (x < temp) ...{

                    temp = x;

                    place = Integer.parseInt(items[i]);   }   }

            System.out.println("place: " + place);

            io.close();

            System.exit(0);

        } catch (IOException e) ...{

            e.printStackTrace(); }   }}

10.使用Java,long.Math类,生成10个0到99之间的随即整数,求出它们中的最小值和最大值*/

package exec;

import java.util.Iterator;

import java.util.TreeSet;

public class RandomNumber ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        /** *//**方法1

        long max = 50;

        long min = 50;

        for(int i=0; i<10; i++){

            long number = Math.round(Math.random()*99 + 1);

            System.out.print(number + " ");

            max = Math.max(max, number);

            min = Math.min(min, number);

            if(i == 9){

                System.out.print(" Math MaxNumber=" + max + " MinNumber=" + min);     }       }

        //方法2

        TreeSet ts = new TreeSet();

        for(int i=0; i<10; i++)...{

            long number = Math.round(Math.random()*99 + 1);

            System.out.print(number + " ");

            ts.add(number);

        }

        System.out.println();

        Iterator it = ts.iterator();

        while(it.hasNext())...{

            System.out.print(it.next() + " ");       }

        System.out.print(" Math MaxNumber=" + ts.last() + " MinNumber=" + ts.first());}}

11.假设有一条钢材长2000米,每天截取其中的一半,编写一程序求出多少天后,钢材的长度小于5米.*/

package exec;

public class SteelSection ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        int i = 0;

        float steel = 2000f;

        while (steel >= 5) ...{

            i++;

            steel = steel / 2;

            System.out.println(i + "天后钢管长" + steel + "米"); }   }}

12.完全数是指其所有因子(包括1但不包括该数自身)的和等于该数,例如28=1+2++4+7+14,28就是一个完全数. * 编写一个程序求出2到10000之间的所有完全数.*/

package exec;

public class WanNumber ...{

    public static void main(String[] args) ...{

        // TODO Auto-generated method stub

        int m = 0;

        for (int n = 2; n <= 10000; n++) ...{

            m = 0;

            for (int i = 1; i < n; i++) ...{

                if (n % i == 0) ...{

                    m += i;

                    //if (m == n) ...{ System.out.println(n + "个完全数"); }

               }  

         }if (m == n) ...{ System.out.println(n + "个完全数"); }  } }}

//////////////////////////////

              int n,sum =0;

                for ( int i = 2; i <= 10000;i++)

                {

                       sum =0;

                       for ( int j = 1;j < i; j++)