Return true if all items in the first array occurs in the second array

Question

I have a generic method

public static <T> boolean lessThanOrEqualTo(T[] arr1, T[] arr2) {

    for(int i = 0; i < arr1.length; i++) {
    T current = arr1[i];
    boolean[] track = new boolean[arr2.length];
    for(int j = 0; j < arr2.length; j++) {

        track[j] = current.equals(arr2[j]);

        if(j == arr2.length-1) {
            for(int k = 0; k < track.length; k++) {
                if(track[k] == true) {
                    System.out.println(Arrays.toString(track));
                    return true;
                }
            }
        }
    }
    System.out.println(Arrays.toString(track));
}
return false

}

I have to return true if every item in arr1 is inside arr2.

Example:

lessThanOrEqualTo({ "Bill", "Mark", "Bill", "Mark", "Bill"}, 
 {"Bill", "Alex", "Mark"});

returns true because every item of arr1 is in arr2.

How can I go about this problem?

Why did you name it *`lessThanOrEqualTo`*? Seems a bit misleading — Michael, Nov 24 '15 at 17:11
what did this give compilation error, exception , or unexpected result please mention that — Ramanlfc, Nov 24 '15 at 17:23
My code always returns true when I compile. I tried different cases where not all the names in arr1 are in arr2 and it still returns true. — , Nov 24 '15 at 17:28
Possible duplicate of [best way to compare between two-dimension integer arrays in java](http://stackoverflow.com/questions/2555753/best-way-to-compare-between-two-dimension-integer-arrays-in-java) — Norbert, Nov 24 '15 at 17:28

score 1 · Answer 1 · answered Nov 24 '15 at 17:25

1

Here is the solution using Set

public static <T> boolean lessThanOrEqualTo(T[] arr1, T[] arr2) {
   Set<T> a = new HashSet<>(Arrays.asList(arr1));
   Set<T> b = new HashSet<>(Arrays.asList(arr2));
   a.removeAll(b);
   return a.isEmpty();
}

answered Nov 24 '15 at 17:25

Ashraful Islam

12,470
3
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score 0 · Accepted Answer · answered Nov 24 '15 at 17:25

0

one way of doing it is to use Set. in terms of speed its probably slower, but easier to understand.

public static <T> boolean lessThanOrEqualTo(T[] arr1, T[] arr2) {
  Set<T> firstSet=new HashSet<T>(Arrays.asList(arr1));
  Set<T> secondSet=new HashSet<T>(Arrays.asList(arr2));
  int countOfFirst=firstSet.size();
  firstSet.retainAll(secondSet);
  return firstSet.size() == countOfFirst;
}

answered Nov 24 '15 at 17:25

nafas

5,283
3
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This worked nicely, however, I dont understand how it's working. – Nov 24 '15 at 17:33
@CodeDexter hmm, have a read through this document, hopefully it gives a notion of what set is: http://docs.oracle.com/javase/7/docs/api/java/util/Set.html – nafas Nov 25 '15 at 09:14

Return true if all items in the first array occurs in the second array

2 Answers2