Sorting an array using recursion in java

Problem:

Write an method that sorts an array using recursion in Java

Output:

Not applicable.

Solution:

public static void sort(double[] list) {
  sort(list, list.length - 1);
  }
 
  public static void sort(double[] list, int high) {
  if (high > 1) {
  // Find the largest number and its index
  int indexOfMax = 0;
  double max = list[0];
 for (int i = 1; i <= high; i++) {
 if (list[i] > max) {
 max = list[i];
 indexOfMax = i;
 }
 }
 // Swap the largest with the last number in the list
 list[indexOfMax] = list[high];
 list[high] = max;
 // Sort the remaining list
 sort(list, high - 1);
 }

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Sorting a Two-dimensional Array in Java

Problem:

In a simple java problem, create a two-dimensional array, and fill it with random numbers. Then sort it.

Solution:

import java.util.Scanner;
public class TwoDimensional
{
  public static void main (String[] args)
  {
    int[][] nums = { {6,4,8,1},

                      {64,76,1,7},

                      {43,87,23,45},

                      {100,56,233,5}};
    int temp =0;//For later use
    int j=0,k =0;
    for (int i =0;i<nums.length*nums[0].length;i++)
    {
      for (j =0;j<nums.length;j++)
      {
        for (k =0;k<nums[j].length-1;k++)
        {
          if (nums[j][k] > nums[j][k+1])
          {
            temp = nums[j][k];
            nums[j][k] = nums[j][k+1];
            nums[j][k+1] = temp;
          }
        }
        if (j != nums.length-1 && nums[j][k] > nums[j+1][0])
        {
          temp = nums[j][k];
          nums[j][k] = nums[j+1][0];
          nums[j+1][0] = temp;
        }
      }
    }
    for (int i = 0;i<nums.length;i++)
    {
      for (j =0;j<nums[i].length;j++)
      {
        System.out.print(nums[i][j] +" ");
      }
      System.out.println();
    }
  }
}

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Sorting two-dimensional array in java

This exercise can be found in the book "Introduction to Java Programming - 8th edition" by Y. Daniel Liang. No copyright infringement intended.

(Sorting two-dimensional array) Write a method to sort a two-dimensional array using following header:

public static void sort(int m[][])

The method performs a primary sort on rows and a secondary sort on columns

import java.util.Scanner; public class SortingTwoDimensionalArray {   public static int[][] sort(int[][] m)   {     for (int i =0;i<m.length;i++)     {       for (int j =0;j<m.length-1;j++)       {       if (m[j][0] >m[j+1][0])       {         int temp = m[j][0];         int temp1 = m[j][1];         m[j][0]= m[j+1][0];         m[j][1]= m[j+1][1];         m[j+1][0] = temp;         m[j+1][1] = temp1;       }              if (m[j][0] == m[j+1][0])       {         if(m[j][1] >m[j+1][1])         {           int temp3 = m[j][1];           m[j][1] = m[j+1][1];           m[j+1][1] = temp3;         }       }       }     }     return m;   }   //Just a test   public static void main (String[] args)   {     int[][] m = { {4,2},{1,7},{4,5},{1,2},{1,1},{4,1}};     sort(m);     for (int i =0;i<m.length;i++)     {       for (int j =0;j<m[i].length;j++)       {         System.out.print(m[i][j] + " ");         }       System.out.println();     }   } }

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Computing the Weekly Hours for Each Employee in Java

Problem:

Suppose the weekly hours for all employees are stored in a two-dimensional array. Each row records an employee’s seven-day work hours with seven columns. For example, the array shown below stores the work hours for eight employees. Write a program that displays employees and their total hours in decreasing order of the total hours.

Output:

2 3 4 4 5 8 8
7 3 4 3 3 4 4
3 3 4 3 3 2 2
9 3 4 7 3 4 1
3 5 4 3 6 3 8
3 4 4 6 3 4 4
3 7 4 8 3 8 4
6 3 5 9 2 7 9
Employee's 7 worked the most with 41 hours
Employee's 6 worked the most with 37 hours
Employee's 0 worked the most with 34 hours
Employee's 4 worked the most with 32 hours
Employee's 3 worked the most with 31 hours
Employee's 1 worked the most with 28 hours
Employee's 5 worked the most with 28 hours
Employee's 2 worked the most with 20 hours

Solution:

import java.util.Scanner;
public class WeeklyHour
{
  public static int[][] readHours()
  {
    Scanner scan = new Scanner (System.in);
    int[][] employees = new int[8][7];
    for (int i =0;i<employees.length;i++)
    {
      for (int j =0;j<employees[i].length;j++)
      {
        employees[i][j] = scan.nextInt();
      }
    }
    return employees;
  }
  public static int[][] sortEmployees(int[][] employees)
  {
    int[][] tempar = new int[8][2];
    for (int i =0;i<employees.length;i++)
    {
      tempar[i][0] =i;
      for (int j=0;j<employees[i].length;j++)
      {
        tempar[i][1] += employees[i][j]; 
      }
    }
    for (int i =0;i<employees.length;i++)
    {
      for (int j =0;j<employees.length -1;j++)
      {
        if ( tempar[j][1] < tempar[j+1][1] )
        {
          int temp = tempar[j][1];
          int temp2 = tempar[j][0];
          
          tempar[j][1] = tempar[j+1][1];
          tempar[j][0] = tempar[j+1][0];
          tempar[j+1][1] = temp;
          tempar[j+1][0] = temp2;
        }
      }
    }
    return tempar;
  }
  
  public static void printEmployees(int[][] tempar)
  {
    for (int i =0;i<tempar.length;i++)
    {
        System.out.println("Employee's " + tempar[i][0] +
                    " worked the most with " + tempar[i][1] + " hours" );
    }
  }
  
  public static void main (String[] args)
  {
    int[][] nums = readHours();
    int[][] nums1 = sortEmployees(nums);
    printEmployees(nums1);
  }
}

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Sorting an Integer Array in Java

Problem:

Write a program that reads 10 value of integers from the user, store them in an array of integers. Then print the reverse of this array. Later, print a sorted version of the user. You are not allowed to use the Arrays.sort() method.

Output:

Enter the values: 1 6 3 4 2 9 8 10 5 7
Reversed array: 7 5 10 8 9 2 4 3 6 1
Values sorted: 1 2 3 4 5 6 7 8 9 10
-2

Solution:

import java.util.Scanner;
 
public class Problem2
{
 public static void main (String[] args)
 {
 Scanner scan = new Scanner(System.in);
 System.out.print("Enter the values: ");
 int[]list = new int[10];
 for (int i=0; i <10; i++)
 {
  list[i]= scan.nextInt();
 }
 System.out.print("Reversed array:  " );
 for(int k =9; k>=0;k--)
  System.out.print(list[k] + " ");
 
 for (int d=0;d<10;d++)
 {
  for (int i =0; i<9;i++)
  {
   if(list[i]>list[i+1])
   {
   int greater = list[i];
   list[i] = list[i+1];
   list[1+i]= greater;
   }
  }
 }
 System.out.println();
 System.out.print("Values sorted:   ");
 for(int values :  list)
  System.out.print(values + " ");
}
}

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