Write a program to detect duplicate elements in array?

Answer 1

The simplest way of doing this is not very efficient, but provides a quick development time. You want to take all of the elements of the array, add them to a Set, then retrieve them as an array again. Note that this will probably not preserve the order of elements in the array.

{

Object[] originalArray; // let's pretend this contains the data that

// you want to delete duplicates from

Set newSet = new HashSet();

for (Object o : originalArray) {

newSet.add(o);

}

// originalArray is now equal to the array without duplicates

originalArray = newSet.toArray();

}

Now the efficient, and more correct, solution.

This one will create a new array of the correct size without duplicates.

{

Object[] originalArray; // again, pretend this contains our original data

// new temporary array to hold non-duplicate data

Object[] newArray = new Object[originalArray.length];

// current index in the new array (also the number of non-dup elements)

int currentIndex = 0;

// loop through the original array...

for (int i = 0; i < originalArray.length; ++i) {

// contains => true iff newArray contains originalArray[i]

boolean contains = false;

// search through newArray to see if it contains an element equal

// to the element in originalArray[i]

for(int j = 0; j <= currentIndex; ++j) {

// if the same element is found, don't add it to the new array

if(originalArray[i].equals(newArray[j])) {

contains = true;

break;

}

}

// if we didn't find a duplicate, add the new element to the new array

if(!contains) {

// note: you may want to use a copy constructor, or a .clone()

// here if the situation warrants more than a shallow copy

newArray[currentIndex] = originalArray[i];

++currentIndex;

}

}

// OPTIONAL

// resize newArray (using _newArray) so that we don't have any null references

Object[] _newArray = new Object[currentIndex];

System.arraycopy(newArray, 0, _newArray, 0, currentIndex);

}

Answer 2

printf( "Enter 20 integers between 10 and 100:\n");

15

16 /* get 20 integers from user */

17 for( i = 0; i <= MAX- 1; i++ ) {

18 duplicate = 0;

19 scanf( "%d", &value );

20

21 /* test if integer is a duplicate */

22 for( j = 0; j < k; j++ ) {

23

24 /* if duplicate, raise flag and break loop */

25 if( value == a[ j ] ) {

26 duplicate = 1;

27 break;

28 } /* end if */

29

30 } /* end for */

31

32 /* if number is not a duplicate enter it in array */

33 if( !duplicate ) {

34 a[ k++ ] = value;

35 } /* end if */

36

37 } /* end for */

38

39 printf( "\nThe nonduplicate values are:\n");

40

41 /* display array of nonduplicates */

42 for( i = 0; a[ i ] != 0; i++ ) {

43 printf( "%d ", a[ i ] );

44 } /* end for */

45

46 printf( "\n");

47

48 return 0; /* indicate successful termination */

49

50 }

Answer 3

Basically you have to compare each array element to every other array element. This can be done with a nested loop. For example, in Java: for (int i = 0; i