import java.util.Map;
import java.util.HashMap;
class FindElementThatAppearsOnceInArray_Java {
public static int findElementThatAppearsOnceInArray(int[] arr) {
Map<Integer, Integer> map = new HashMap<>();
for (int x : arr) {
map.put(x, map.getOrDefault(x, 0) + 1);
}
for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
if (entry.getValue() == 1) {
return entry.getKey();
}
}
return -1;
}
public static void main(String[] args) {
int arr[] = new int[]{3, 5, 5, 2, 7, 3, 2, 8, 8, 3, 2, 5, 8};
System.out.println(findElementThatAppearsOnceInArray(arr));
}
}
/*
run:
7
*/