Array Reverse Using Java

In this article we are discuss about Basic Problem in Programming. How To Reverse a Array Elements.

Reverse a given array elements. For example1,

[1,2,3,4,5]

Output

[5,4,3,2,1]

example2,

Input

[3,5,1,2,4]

Output

[4,2,1,5,3]

1) With Extra Space (Copy Arrar)

We can simple make a same size of array and copy from given array elements to new array variable.

Its takes o(n) Time Complexity. And more Space To Run Programme.

class arrayReverse{

    public static void main(String[] args){

        int[] arr={1,2,3,4,5};

        int n=arr.length;

        int[] brr=new int[n];

        for(int i=0;i<n;i++){

            brr[i]=arr[n-i-1];

}

        for(int j=0;j<n;j++){

            System.out.println(brr[j]);

}

}

}

2)With Out Extra Space.

We can Swap The Array Element One By One. Like First Element And Last. Second Element And Second Last Until Reach Middle Element.

class arrayReverseWithoutExtraSpace{

    public static void main(String[] args){
        int[] arr={1,2,3,4,5,6};
        int n=arr.length;
        int i=0;
        int j=n-1;
        while(i<j){
            int temp=arr[i];
            arr[i]=arr[j];
            arr[j]=temp;
            i+=1;
            j-=1;
        }

        for(int k=0;k<n;k++){
            System.out.println(arr[k]);
        }
    }
}

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