How to take input from user in the following format in java?

Question

👉🏻Input Format :-  First line will be the number of testcases, T. Next line will have T integers, denoted by N.

Sample Input :- 2
3 15

Like over here in the first line we have 2 which is the value of T(no. of testcases) and in the next line we have T number of integers and since over here T = 2 therefore we are having 2 integers 3 and 15. So, basically I want to ask that how do we take multiple inputs from user in a single line separated by space in Java using Scanner class ?

I'm a complete beginner in competitive programming and was trying to solve a problem from hackerrank where they usually ask for this type of input from the user. I googled it but could not find something productive. So, can anyone help me in understanding this input format?

Answer 1

Smriti Kaur Not sure whether this will meet the Competitive programming input time limits.

Or this link might help.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.tutorialspoint.com/how-to-input-multiple-values-from-user-in-one-line-in-java&ved=2ahUKEwjczbDuvLnrAhWJXSsKHdnYAc4QFjANegQICBAB&usg=AOvVaw3ixSM1ZmYSKXYB2VNCMwvn

import java.util.*;
public class Program
{
public static void main(String[] args) {
int t = 0;
Scanner in= new Scanner(System.in);
t = in.nextInt();
int[] n = new int[t];

for(int i = 0; i < t; i++)
n[i] = in.nextInt();

System.out.println(t);
for(int i =0; i<n.length;i++ )
System.out.print(n[i]+" ");
}
}

/*
copy paste one of this as input(input format)

2
1 2

3
1 2 3

9
1 2 3 4 5 6 7 8 9
*/

Answer 2

For reading an Integer in java,.
Scanner inp = new Scanner(System.in);
now using scanner inject 'inp', you can read all data types...
For integer, inp.nextInt(); it will take a next, int value from input stream (whether it is in next line or after a space).
nexrLine(); read the entire line as a string from the next position of input.
Ex:
int a = inp.nextInt();
int b = inp.nextInt();
For this, you can input as 2 3
Or as
2
3

int a = inp.nextInt();
String st = inp.nextLine();
For these, if input is 2 3 4,
then a =2, st = "3 4";
if input is
2
3 4 then a =2 and st =""; you last input "3 4".

So by nextInt() you can take multiple input by space separating in a single line.. By next(); also for single word of input.....
(edited)

Answer 3

So, that means the following snippet of code can be used for taking input from the user according to the input format i.e., 2 in the first line two space separated integers 3 15 in the second line?⬇️

Scanner sc = new Scanner(System.in)
int T = sc.nextInt( );
for(int i =1;i<=T;i++)
{
int N = sc.nextInt( );
}

Answer 4

You can take the first input and store it in variable T then by using Scanner class's object you can take multiple inputs inside a loop that will depend on the value of T. And for your question about taking input in single line, you can go through the question attached below.
Thank you
https://stackoverflow.com/questions/23506429/how-to-read-multiple-integer-values-from-a-single-line-of-input-in-java

Answer 5

a user has to respects this format too.
he writes number eg 5 and presses enter

then he writes some numbers and spaces, in this example 5 times because the first number was 5
1 2 3 40 50

the program scans it by methods of Scanner:

int t = scanner.nextInt(); // for first number
while(t-- > 0)
System.out.println( scanner.nextInt() ); // for print other numbers

instead of print, usually you need store numbers to an array or variables

Answer 6

Jayakrishna🇮🇳 but what is "System inp = new System (System.in); "? I mean u have wriiten it intentionally or by mistake u have typed "System" instead of "Scanner"?

Answer 7

Smriti Kaur yes. sry for that. It's typo mistake..
So correct one is
Scanner inp = new Scanner(System.in);
Yes. That code works for reading..
[Take initialization out to retain N value..]

Answer 8

zemiak oh okay but then where should I scann EOL to avoid this , after inputting T ?

Answer 9

Jayakrishna🇮🇳 oh okay thanks and there's no need for sorry...

Answer 10

Thank you all for helping me out...🎉
Jayakrishna🇮🇳
zemiak
RKK
Hardik Sharma

Answer 11

Kaur I checked it, and it works ok .., sometimes it is problem, but not here

Answer 12

Ok so from all this discussion can I conclude that the following code will only use "two" and not "three" lines of input in the input file that is generated in the Hackerrank platform ?

Scanner sc = new Scanner(System.in)
int T = sc.nextInt( );
for(int i =1;i<=T;i++)
{
int N = sc.nextInt( );
}

Answer 13

Jayakrishna🇮🇳 yes u r absolutely right about the code playground but I want the answer in reference to the IDE used by Hackerrank or hackerearth...that whether the aforementioned code snippet will use 2 lines of input or 3 lines of input ? In the question which they have asked they want the user to use only two lines of input first one contains the value of T and the second line will have T numbers of space separated integers. So, altogether it want 3 inputs from the user (if the value of T is 2) but we are allowed to use only 2 lines of input and not 3 ? I hope now my question is clear?😅

Answer 14

Smriti Kaur I think, That description means, just first value representing number of values to be given should be taken to T, and next are values..
So if T =2, you can take input on i=1,2 values into N..
If T=3, you can take, input into N, for i=1,2,3,..
So code snippet works like,
Accepting T number of values into N..
Since all intigers , number of lines no effect. If input contains a line of string values, there may comes problems...
And is it getting wrong there anything? Did you checked it?

Answer 15

Jayakrishna🇮🇳 no I haven't checked it yet... but I think now my doubt is clear. Actually, I got confused in understanding the input format.

Answer 16

Smriti Kaur actually in that code snippet, number of input lines doesn't matter.. Check it in code playground by taking input in differet ways..