//Given an array of integers, every element appears three times except for one,

//which appears exactly once. Find that single one.

//Note:

//Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

class SingleNumberII {

public int singleNumber(int[] nums) {

HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();

for(int i: nums) {

if(map.containsKey(i)) {

map.put(i, map.get(i) + 1);

} else {

map.put(i, 1);

}

}

for(int key: map.keySet()) {

if(map.get(key) == 1) {

return key;

}

}

//no unique integer in nums

return -1;

}

}