Multiline input in Java

Question

I am trying to read an input like this:

5 3 3
1 2 3 4 5
5 4 3 2 1

When I use the scanner and try something like this:

        Scanner sc = new Scanner(System.in); 
        int n, x, y; 
        String[] temp = sc.nextLine().split(" "); 
        n = Integer.parseInt(temp[0]); 
        x = Integer.parseInt(temp[1]); 
        y = Integer.parseInt(temp[2]);

        int[] a, b; 
        a = b = new int[n];

        String[] t = sc.nextLine().split(" ");
        for(int i = 0; i < n; i++){
            a[i] = Integer.parseInt(t[i]); 
        }
        String[] f = sc.nextLine().split(" ");
        for(int i = 0; i < n; i++){
            b[i] = Integer.parseInt(f[i]); 
        }

This just prints that the arrays 'a' and 'b' are same;

[5, 4, 3, 2, 1]
[5, 4, 3, 2, 1]
12

How can I read this input?

Answer 1

The problem with your code is not how you read the input, but this line here:

a = b = new int[n];

In this line, you set a and b to the same new int array. You did create a new array here, but you only created one. Both a and b refer to that same one. So when you are doing b[i] =... , you are in fact overwriting the values you've just written to it in the first loop.

You should create two arrays:

a = new int[n];
b = new int[n];

Note that another way to read the input is to use nextInt , but your way is okay too.

Scanner sc = new Scanner(System.in); 
int n, x, y;
n = sc.nextInt();
x = sc.nextInt();
y = sc.nextInt();

int[] a, b; 
a = new int[n];
b = new int[n];

for(int i = 0; i < n; i++){
    a[i] = sc.nextInt();
}
for(int i = 0; i < n; i++){
    b[i] = sc.nextInt();
}

Answer 2

This is causing the problem.

a = b = new int[n];

Both a, b are referencing the same array object. Hence, the later input is overriding the previous input. Change this to:

a = new int[n];
b = new int[n];