日拱一卒

1 一周见闻

1.1 技术文章

1.2 泛互联网文章

2 技术总结

3 Algorithm(算法题)

class Solution {
    public int openLock(String[] deadends, String target) {
        Set<String> deadLocks = new HashSet<>();
        for(String str : deadends) {
            deadLocks.add(str);
        }
        Set<String> visited = new HashSet<>();
        Deque<String> queue = new ArrayDeque<>();

        int step = 0;
        queue.offer("0000");
        visited.add("0000");
        while(!queue.isEmpty()) {
            int size = queue.size();
            for(int i = 0; i < size; i++) {
                String cur = queue.poll();
                if(deadLocks.contains(cur)) {
                    continue;
                }
                if(target.equals(cur)) {
                    return step;
                }

                for(int j = 0; j < 4; j++) {
                    String up = plusOne(cur, j);
                    if(!visited.contains(up)) {
                        queue.offer(up);
                        visited.add(up);
                    }
                    String down = minusOne(cur, j);
                    if(!visited.contains(down)) {
                        queue.offer(down);
                        visited.add(down);
                    }
                }
            }
            step++;
        }
        return -1;
    }

    public String plusOne(String cur, int j) {
        char[] ch = cur.toCharArray();
        if(ch[j] == '9') {
            ch[j] = '0';
        } else {
            ch[j] += 1;
        }
        return new String(ch);
    }

    public String minusOne(String cur, int j) {
        char[] ch = cur.toCharArray();
        if(ch[j] == '0') {
            ch[j] = '9';
        } else {
            ch[j] -= 1;
        }
        return new String(ch);
    }
} 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head == null || head.next == null) {
            return head;
        }
        ListNode dummy = new ListNode(-101);
        ListNode p1 = dummy;
        ListNode p2 = head;
        while(p2 != null) {
            if(p2.next != null && p2.val == p2.next.val) {
                while(p2.next != null && p2.val == p2.next.val) {
                    p2 = p2.next;
                }
                p2 = p2.next;
                if(p2 == null) {
                    p1.next = null;
                }
            } else {
                p1.next = p2;
                p1 = p1.next;
                p2 = p2.next;
            }
        }
        return dummy.next;
    }
}