 Compsciguy - 4 years ago 137
Java Question

# Merge two arrays and remove duplicates in Java

I am having trouble removing the duplicates from two arrays that have been merged into one. I have written the following code that merges the arrays, yet I'm not sure how to remove the duplicates from the final array. Assume the arrays are already sorted.

``````public static int[] merge(int[] list1, int[] list2) {
int[] result = new int[list1.length + list2.length];

int i = 0;
int j = 0;

for (int k = 0; k < (list1.length + list2.length); k++) {
if (i >= list1.length) {
result[k] = list2[j];
j++;
}
else if (j >= list2.length) {
result[k] = list1[i];
i++;
}
else {
if (list1[i] < list2[j]) {
result[k] = list1[i];
i++;
} else {
result[k] = list2[j];
j++;
}
}
}
return result;
}
`````` badperson
Answer Source

Ok, someone hated all the answers. Here's another attempt that combines two stackoverflow q's, combining arrays and removing dupes.

This one runs a good deal faster than my earlier attempt on two lists of a million ints.

``````public int[] mergeArrays2(int[] arr1, int[] arr2){
int[] merged = new int[arr1.length + arr2.length];
System.arraycopy(arr1, 0, merged, 0, arr1.length);
System.arraycopy(arr2, 0, merged, arr1.length, arr2.length);

Set<Integer> nodupes = new HashSet<Integer>();

for(int i=0;i<merged.length;i++){
nodupes.add(merged[i]);
}

int[] nodupesarray = new int[nodupes.size()];
int i = 0;
Iterator<Integer> it = nodupes.iterator();
while(it.hasNext()){
nodupesarray[i] = it.next();
i++;
}

return nodupesarray;
}
``````

console output:

``````INFO [main] (TestMergeArray.java:40) - creating two lists of a million ints
DEBUG [main] (TestMergeArray.java:41) - list 1 size : 1000000
DEBUG [main] (TestMergeArray.java:42) - list 2 size : 1000000
INFO [main] (TestMergeArray.java:56) - now merging
INFO [main] (TestMergeArray.java:59) - done, final list size is 864975
``````
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