Loop over the given array of strings to build a result string like this: when a string appears the 2nd, 4th, 6th, etc. time in the array, append the string to the result. Return the empty string if no string appears a 2nd time.
wordAppend(["a", "b", "a"]) → "a"
wordAppend(["a", "b", "a", "c", "a", "d", "a"]) → "aa"
wordAppend(["a", "", "a"]) → "a"
Solution:
public String wordAppend(String[] strings) {
Map<String, Integer> map = new HashMap<String, Integer>();
String holder = "";
for(int i=0; i<strings.length; i++){
if(map.get(strings[i]) == null){
map.put(strings[i], 1);
}else{
map.put(strings[i], map.get(strings[i])+1);
if(map.get(strings[i])%2 == 0){
holder+=strings[i];
}
}
}
return holder;
}