JAVA ARRAY NOTES_day-2

best Program practise in arrays
Q6) WAP to find the Maximum Element in the Array

public class MaxElement {
public static void main(String[] args) {

    int[] arr = {12, 45, 7, 89, 34};

    int max = arr[0];

    for(int num : arr) {
        if(num > max) {
            max = num;
        }
    }

    System.out.println("Maximum Element = " + max);
}

}

✔ Compare each element
✔ Store the largest value

Q7) HEAP and STACK Diagram

Array objects are created in the heap memory.

Example:

int[] arr = new int[5];
HEAP MEMORY

1000x: ArrayObject [0, 0, 0, 0, 0]

STACK MEMORY

arr → 1000x

✔ Stack → Reference variable

✔ Heap → Actual Array Object

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Q8) Modify Array Element

import java.util.Arrays;

class ArrayElementModification {

    public static int[] modifyElement(int[] arr) {

        arr[0] = 100;
        arr[1] = 200;
        arr[2] = 300;

        return arr;
    }
}

public class ArrayExDemo8 {

    public static void main(String[] args) {

        int[] val = {10,20,30,40,50};

        System.out.println("Original Array : " + Arrays.toString(val));

        int[] modified = ArrayElementModification.modifyElement(val);

        System.out.println("After Modification : " + Arrays.toString(modified));
        System.out.println("Original Array is : " + Arrays.toString(val));
    }
}

✔ Arrays are passed by reference
✔ Changes reflect in othe riginal array

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Q9) Bubble Sort (Ascending Order)
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java

import java.util.Arrays;

public class BubbleSortDemo {

public static void main(String[] args) {

    int[] arr = {20, 10, 30, 40, 50, 90};

    for(int i = 0; i < arr.length; i++) {
        for(int j = i + 1; j < arr.length; j++) {

            if(arr[i] > arr[j]) {
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }
    }

    System.out.println("Sorted Array : " + Arrays.toString(arr));
}

}

✔ Time Complexity → O(n²)

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Q10) Search Element (Linear Search)

public class SearchElement {

    public static void main(String[] args) {

        int[] arr = {20,30,10,50,90,30};
        int target = 30;

        for(int i = 0; i < arr.length; i++) {
            if(arr[i] == target) {
                System.out.println("Element found at index : " + i);
            }
        }
    }
}

✔ Linear Search → O(n)

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Q11) Find Duplicate Elements
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java

public class DuplicateDemo {

public static void main(String[] args) {

    int[] arr = {2,3,9,2,8,7,3,2};

    for(int i = 0; i < arr.length; i++) {
        for(int j = i + 1; j < arr.length; j++) {

            if(arr[i] == arr[j]) {
                System.out.println("Duplicate Element : " + arr[i]);
            }
        }
    }
}

}

✔ Nested Loop → O(n²)

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Q11) Remove Duplicate Elements

public class RemoveDuplicate {

    public static void main(String[] args) {

        int[] arr = {2,3,9,2,8,7,3,2};

        for(int i = 0; i < arr.length; i++) {
            for(int j = i + 1; j < arr.length; j++) {
                if(arr[i] == arr[j]) {
                    arr[j] = -1;
                }
            }
        }

        for(int num : arr) {
            if(num != -1) {
                System.out.print(num + " ");
            }
        }
    }
}
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Q12) Insert Element at Last Position
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java

import java.util.Arrays;

class InsertAtLast {

public static int[] insertLast(int[] arr, int element) {

    int[] newArr = new int[arr.length + 1];

    for(int i = 0; i < arr.length; i++) {
        newArr[i] = arr[i];
    }

    newArr[newArr.length - 1] = element;

    return newArr;
}

}

Q13) Insert Element at Middle Position

java

class InsertAtMiddle {

    public static int[] insertMiddle(int[] arr, int element) {

        int[] newArr = new int[arr.length + 1];
        int middle = arr.length / 2;

        for(int i = 0; i < middle; i++) {
            newArr[i] = arr[i];
        }

        newArr[middle] = element;

        for(int i = middle; i < arr.length; i++) {
            newArr[i + 1] = arr[i];
        }

        return newArr;
    }
}
Q14) Merge Two Arrays
import java.util.Arrays;

class Merge {

    public static int[] mergeArrays(int[] x, int[] y) {

        int[] newArr = new int[x.length + y.length];
        int position = 0;

        for(int element : x) {
            newArr[position++] = element;
        }

        for(int element : y) {
            newArr[position++] = element;
        }

        return newArr;
    }
}


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                🔥 FINAL SUMMARY 🔥
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✔ Max → Compare and update
✔ Modify → Arrays are reference type
✔ Sort → Nested loop
✔ Search → Linear scan
✔ Duplicate → Compare pairs
✔ Insert → Create new array
✔ Merge → Create bigger array