CODEWITHSUNDEEP
javaarrays
Andrew Argie
Andrew Argie

Reputation: 45

Loop not properly modifying array elements

The loop causing issues is the second for loop.

import java.util.Scanner;
public class StudentScores {
   public static void main (String [] args) {
      Scanner scnr = new Scanner(System.in);
      final int NUM_POINTS = 4;
      int[] dataPoints = new int[NUM_POINTS];
      int controlValue;
      int i;

      controlValue = scnr.nextInt();

      for (i = 0; i < dataPoints.length; ++i) {
         dataPoints[i] = scnr.nextInt();
      }

      for (i = 0; dataPoints[i] < controlValue; ++i) {
         dataPoints[i] = dataPoints[i] * 2;
      }

      for (i = 0; i < dataPoints.length; ++i) {
         System.out.print(dataPoints[i] + " ");
      }
      System.out.println();
   }
}

Currently when i run the test, this is what pops up.

Testing with inputs: 10 2 12 9 20

Output differs.

Your output

4 12 9 20

Expected output

4 12 18 20

the first number in the list of inputs is the maximum number it should multiply by 2. Since 20 is > 10, it is not multiplied. However 9 should be multiplying to 18, but it is not. If anyone could give some insight into anything i might be doing wrong when forming this loop, I would greatly appreciate it. Thank you!

Upvotes: 2

Views: 450

Answers (1)

segFault
segFault

Reputation: 4054

Your second for loop is exiting because of the condition and the order of your input data, and will stop when a control value is reached. For example, if you instead had an input of 10 1 2 3 4, you would get the results you expect (ie. 2 4 6 8), but your for loop is exiting when the condition dataPoints[i] < controlValue is reached (in your case at 12).

Instead you should loop through the entire dataPoints array, as you do in your 3rd loop, and check the controlValue before doubling the values.

import java.util.Scanner;
public class StudentScores {
   public static void main (String [] args) {
      Scanner scnr = new Scanner(System.in);
      final int NUM_POINTS = 4;
      int[] dataPoints = new int[NUM_POINTS];
      int controlValue;
      int i;

      controlValue = scnr.nextInt();

      for (i = 0; i < dataPoints.length; ++i) {
         dataPoints[i] = scnr.nextInt();
      }

      for (i = 0; i < dataPoints.length; ++i) {
         if (dataPoints[i] < controlValue) {
             dataPoints[i] = dataPoints[i] * 2;
         }
      }
      
      // This could be combined into the loop above...
      for (i = 0; i < dataPoints.length; ++i) {
         System.out.print(dataPoints[i] + " ");
      }
      System.out.println();
   }
}

You could also do all of this in a single loop if you wanted to, for example:

for (i = 0; i < dataPoints.length; ++i) {
    dataPoints[i] = scnr.nextInt();

    if (dataPoints[i] < controlValue) {
        dataPoints[i] = dataPoints[i] * 2;
    }

    System.out.print(dataPoints[i] + " ");
}

Upvotes: 1

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