add

5.leetcode/src/com/fanxb/common/Q19.java

@@ -0,0 +1,41 @@
+package com.fanxb.common;
+
+public class Q19 {
+    public static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode() {
+        }
+
+        ListNode(int val) {
+            this.val = val;
+        }
+
+        ListNode(int val, ListNode next) {
+            this.val = val;
+            this.next = next;
+        }
+    }
+
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+        ListNode p = head, q = head;
+        //先将p,q的距离差拉到n,这样当q在结尾时，刚好p在倒数第n+1个位置上，删除下一个位置即可
+        while ((n--) > 0) {
+            q = q.next;
+        }
+        //考虑特殊情况，当n等于链表长度时，需要删除第一个元素
+        if (q == null) {
+            return p.next;
+        }
+        //让q走到结尾
+        while (q.next != null) {
+            q = q.next;
+            p = p.next;
+        }
+        //删除p的下一个节点
+        p.next = p.next.next;
+        return head;
+
+    }
+}

5.leetcode/src/com/fanxb/common/Q347.java

@@ -0,0 +1,32 @@
+package com.fanxb.common;
+
+import java.util.*;
+
+public class Q347 {
+    public int[] topKFrequent(int[] nums, int k) {
+        Map<Integer, Integer> countMap = new HashMap<>();
+        for (int num : nums) {
+            int count = countMap.getOrDefault(num, 0) + 1;
+            countMap.put(num, count);
+        }
+        PriorityQueue<Integer> res = new PriorityQueue<>(Comparator.comparingInt(countMap::get));
+        for (int num : countMap.keySet()) {
+            if (res.size() < k) {
+                res.add(num);
+            } else if (countMap.get(res.peek()) < countMap.get(num)) {
+                res.poll();
+                res.add(num);
+            }
+        }
+        int[] realRes = new int[k];
+        for (int i = 0; i < k; i++) {
+            realRes[i] = res.poll();
+        }
+        return realRes;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(Arrays.toString(new Q347().topKFrequent(new int[]{1}, 1)));
+    }
+
+}