You have a queue of integers, you need to retrieve the first unique integer in the queue.
Implement the FirstUnique class:
FirstUnique(int[] nums)Initializes the object with the numbers in the queue.int showFirstUnique()returns the value of the first unique integer of the queue, and returns -1 if there is no such integer.void add(int value)insert value to the queue.
Example 1:
Input:
["FirstUnique","showFirstUnique","add","showFirstUnique","add","showFirstUnique","add","showFirstUnique"]
[[[2,3,5]],[],[5],[],[2],[],[3],[]]
Output:
[null,2,null,2,null,3,null,-1]
Explanation:
FirstUnique firstUnique = new FirstUnique([2,3,5]);
firstUnique.showFirstUnique(); // return 2
firstUnique.add(5); // the queue is now [2,3,5,5]
firstUnique.showFirstUnique(); // return 2
firstUnique.add(2); // the queue is now [2,3,5,5,2]
firstUnique.showFirstUnique(); // return 3
firstUnique.add(3); // the queue is now [2,3,5,5,2,3]
firstUnique.showFirstUnique(); // return -1
Example 2:
Input:
["FirstUnique","showFirstUnique","add","add","add","add","add","showFirstUnique"]
[[[7,7,7,7,7,7]],[],[7],[3],[3],[7],[17],[]]
Output:
[null,-1,null,null,null,null,null,17]
Explanation:
FirstUnique firstUnique = new FirstUnique([7,7,7,7,7,7]);
firstUnique.showFirstUnique(); // return -1
firstUnique.add(7); // the queue is now [7,7,7,7,7,7,7]
firstUnique.add(3); // the queue is now [7,7,7,7,7,7,7,3]
firstUnique.add(3); // the queue is now [7,7,7,7,7,7,7,3,3]
firstUnique.add(7); // the queue is now [7,7,7,7,7,7,7,3,3,7]
firstUnique.add(17); // the queue is now [7,7,7,7,7,7,7,3,3,7,17]
firstUnique.showFirstUnique(); // return 17
Example 3:
Input: ["FirstUnique","showFirstUnique","add","showFirstUnique"] [[[809]],[],[809],[]] Output: [null,809,null,-1] Explanation: FirstUnique firstUnique = new FirstUnique([809]); firstUnique.showFirstUnique(); // return 809 firstUnique.add(809); // the queue is now [809,809] firstUnique.showFirstUnique(); // return -1
基础知识没学好，不解释。已经补上了
https://leetcode.com/problems/first-unique-number/discuss/601107/JavaPython-3-DoublyLinkedList-and-LinkedHashSetdict-O(n)-2-neat-codes-w-analysis.
private Set<Integer> unique = new LinkedHashSet<>();
private Set<Integer> total = new HashSet<>();
public FirstUnique(int[] nums) {
for (int n : nums) {
add(n);
}
}
public int showFirstUnique() {
/*
for (int v : unique) {
return v;
}
return -1;
*/
return unique.isEmpty() ? -1 : unique.iterator().next(); // credit to @yelhsabananah
}
public void add(int value) {
if (total.add(value)) {
unique.add(value);
}else {
unique.remove(value);
}
}