Searching and Sorting

Write a program to search an element in array using linear search.

 import java.util.*;

 public class Main {
   public static int linearSearch(int arr[], int key){
     int n=arr.length;
     for(int i=0; i<n;i++){
       if(arr[i]==key){
         return i;
       }
     }
     return -1;
   }
     public static void main(String[] args) {
       int arr[]={5,3,7,1,4,6};
       int key=6;
       System.out.println(linearSearch(arr,key));
   }
 }

Write a program to search an element in sorted array using binary search.

 public class Main { 
     public static int binarySearch(int arr[], int key){ 
         int n= arr.length;
         int start=0; int end= n-1;
         int mid= (start+end)/2; 
         while(start<=end){
             if(arr[mid]==key)
             { return mid; }
             else if(arr[mid]<key)
             { start=mid+1; }
             else if(arr[mid]>key)
             { end= mid-1; }
         } return -1; 
     } 
     public static void main(String[] args)
     {
         int arr[]={1,3,4,5,6,7};
         int key= 4; 
         System.out.println(binarySearch(arr,key)); 
     } 
 }

Write a program to sort an array using bubble sort.

 public class Test {
   public static void sort(int arr[]) {
     int n = arr.length;
     boolean swapped;
     for (int i = 0; i < n - 1; i++) {
       swapped=false;
       for (int j = 0; j < n - 1 - i; j++) {
         if (arr[j] > arr[j + 1]) {
           int temp = arr[j];
           arr[j] = arr[j + 1];
           arr[j + 1] = temp;
           swapped = true;
         }
       }
       if(swapped==false)
         break;
     }
   }

   public static void print(int arr[]) {
     int n=arr.length;
     for (int i = 0; i < n; i++) {
       System.out.print(arr[i] + " ");
     }
   }
   public static void main(String[] args) {
     int arr[] = { 4, 1, 6, 3, 2, 0 };
     sort(arr);
     print(arr);
   }
 }

Write a program to sort an array using selection sort.

Idea:- pick the smallest number from unsorted array and place it at the beginning

 public class Test {
   public static void sort(int arr[]) {
     int n = arr.length;
     for (int i = 0; i < n - 1; i++) {
       int min = i;
       for (int j = i + 1; j < n; j++) {
         if (arr[min] > arr[j]) {
           min = j;
         }
       }
       int temp = arr[min];
       arr[min] = arr[i];
       arr[i] = temp;
     }
   }

   public static void print(int arr[]) {
     int n = arr.length;
     for(int i=0; i<n;i++){
       System.out.print(arr[i] + " ");
     }
   }
   public static void main(String[] args) {
     int arr[] = { 6, 5, 7, 3, 1, 9, 8, 0 };
     sort(arr);
     print(arr);
   }
 }

Write a program to sort an array using insertion sort.

Idea:- Pick an element (from unsorted part) and place in right position in sorted part

 public class InsertionSort {
   public static void insertionSort(int arr[]) {
     for (int i = 1; i < arr.length; i++) {
       int curr = arr[i];
       int prev = i - 1;
       //finding the correct position to insert
       while (prev >= 0 && arr[prev] > curr) {
         arr[prev + 1] = arr[prev];
         prev--;
       }
       //insertion
       arr[prev + 1] = curr;
     }
   }

   public static void printArray(int arr[]) {
     for (int i = 0; i < arr.length; i++) {
       System.out.print(arr[i] + " ");
     }
   }
   public static void main(String[] args) {
     int arr[] = { 5, 4, 1, 3, 2 };
     insertionSort(arr);
     printArray(arr);
   }
 }

Write a program to sort an array using counting sort.

 public class Test {
   public static void Sort(int arr[]) {
     int n = arr.length;
     int largest = Integer.MIN_VALUE;
     for (int i = 0; i < n; i++) {
       if (arr[i] > largest) {
         largest = arr[i];
       }
     }
     int count[] = new int[largest + 1];
     int m = count.length;
     for (int i = 0; i < n; i++) {
       count[arr[i]]++;
     }
     int j = 0;
     for (int i = 0; i < m; i++) {
       while (count[i] > 0) {
         arr[j] = i;
         j++;
         count[i]--;
       }
     }
   }

   public static void print(int arr[]) {
     int n = arr.length;
     for (int i = 0; i < n; i++) {
       System.out.print(arr[i] + " ");
     }
   }
   public static void main(String[] args) {
     int arr[] = {1,4,1,3,2,4,3,7};
     Sort(arr);
     print(arr);
   }
 }

Write a program to sort an array using inbuilt sort method.

 import java.util.*;
 public class Main
 {
     public static void printArrayIncreasing(int arr[]){
         for(int i=0; i<arr.length;i++){
             System.out.print(arr[i]+" ");
         }
     }
     public static void printArrayDecreasing(Integer arr[]){
         for(int i=0; i<arr.length;i++){
             System.out.print(arr[i]+" ");
         }
     }
     public static void main(String[] args) {
         int arr[]={32,33,11,3,5,66};
         Integer arr1[]={32,33,11,3,5,66};
         Arrays.sort(arr);
         printArrayIncreasing(arr);//Increasing order
         Arrays.sort(arr1, Collections.reverseOrder());//Decreasing Order
         System.out.println();
         printArrayDecreasing(arr1);
     }
 }