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I need to make 2 arrays called A and B, both of type int with size 100. Each index should be a random number between 0 and 100 inclusive and then compare both arrays, and say how many times 2 of the same number appeared in both arrays.

This is what I have so far

int count = 0;

int [] A = new int [100];
int [] B = new int [100];

for(int i = 0; i < A.length; i++){
    A [i] = (int)(Math.random()*101);
    System.out.println("Array A: " + i);
}
for(int i = 0; i < B.length; i++){
    B [i] = (int)(Math.random()*101);
    System.out.println("Array B: " + i);
}

if(A [i] == B [i]){
    count++;
}

I'm not sure how to show how many times 2 of the same number appeared in both arrays.

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  • 1
    You will need a third array to hold the results. You would need a compound for-loop, the outer loop will loop over each element in the first array, the inner loop will loop over each element in the second array, comparing each of the elements, each time you find a match, you need to increment the result in the third array Commented Jan 14, 2016 at 23:17

3 Answers 3

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You need to loop through both of the arrays:

int count = 0;

int [] A = new int [100];
int [] B = new int [100];

for(int i = 0; i < A.length; i++){
    A [i] = (int)(Math.random()*101);
    System.out.println("Array A: " + i);
}
for(int i = 0; i < B.length; i++){
    B [i] = (int)(Math.random()*101);
    System.out.println("Array B: " + i);
}

// Loop through the first array
for(int i = 0; i < A.length; i++) {
    // For each element in the first array, loop through the whole second one
    for (int j = 0; j < B.length; j++) {
        // If it's a match
        if(A[i] == B[j])
            count++;
    }
}

System.out.println("Count: " + count);
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Comments

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Alternatively, if you don't need the 2 arrays, you can simply do:

int count = Random.ints(100, 0, 101).boxed().collect(toSet())
                  .retainAll(Random.ints(100, 0, 101).boxed().collect(toSet()))
                  .size();
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You started off nicely, but you need a nested for-loop to check each of the indexes.

ALSO-- make sure that in your arrays you print out A[i] and B[i] otherwise you're just printing out the number of the index as opposed to the number inside the index.

  int count = 0;

  int[] A = new int[100];
  int[] B = new int[100];      

  //Create the first array
  for (int i = 0; i < A.length; i++) {
     A[i] = (int)(Math.random() * 101);
     System.out.println("Array A: " + A[i]);
  }

  //Create the second array
  for (int i = 0; i < B.length; i++) {
     B[i] = (int)(Math.random() * 101);
     System.out.println("Array B: " + B[i]);
  }

  //Check the indexes and make sure they are all compared-- 10,000 comparisons are made
  for (int i = 0; i < A.length; i++) {    
     for (int j = 0; j < B.length; j++) {
        if(A[i] == B[j])
           count++;
     }
  }

Hopefully that posted correctly... first time posting code on this website, but I hope that I was of help!

Keep in mind if the same number is being posted twice, you're going to get counts over 100.

Good luck!

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1 Comment

If all of the element values were zero in A and B, count will be 10000.

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