Java数据结构之Map与Set专篇讲解

public int singleNumber(int[] nums) {
        int single = 0;
        for (int num : nums) {
            single ^= num;
        }
        return single;
    }
 

public int singleNumber(int[] nums){
 
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < nums.length; i++){
            if (set.contains(nums[i])){
                set.remove(nums[i]);
            }else {
                set.add(nums[i]);
            }
        }
        for (int i = 0; i < nums.length; i++){
            if (set.contains(nums[i])){
                return nums[i];
            }
        }
        return -1;
 
    }

 public int numJewelsInStons(String jewels,String stons){
        stons.toUpperCase(Locale.ROOT).toCharArray();
 
        HashSet<Character> set = new HashSet<>();
 
        for (int i = 0; i < jewels.length(); i++){
            set.add(jewels.charAt(i));
        }
 
        int count = 0;
        for (char ch:stons.toCharArray()) {
            if(set.contains(ch)){
                count++;
            }
        }
        return count;
    }

public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String str1 = scan.nextLine();
        String str2 = scan.nextLine();
 
        HashSet<Character> setActual = new HashSet<>();
        for (char ch:str2.toUpperCase(Locale.ROOT).toCharArray()) {
            setActual.add(ch);
        }
        HashSet<Character> setBroken = new HashSet<>();
        for (char ch: str1.toUpperCase(Locale.ROOT).toCharArray()) {
            if(!setActual.contains(ch) && !setBroken.contains(ch)){
                setBroken.add(ch);
                System.out.print(ch);;
            }
        }
    }

class node {
    int val;
    Node next;
    Node random;
 
    public Node(int val) {
        this.val = val;
        this.next = null;
        this.random = null;
    }
}
 
public Node copyRandomList(Node head){
        if (head == null) return null;
        HashMap<Node,Node> map = new HashMap<>();
        Node cur = head;
        while (cur != null){
            Node node = new Node(cur.val);
            map.put(cur,node);
            cur = cur.next;
        }
        cur = head;
        while (cur != null){
            map.get(cur).next = map.get(cur.next);
            map.get(cur).random = map.get(cur.random);
            cur = cur.next;
        }
        return map.get(head);
 
 
    }