Merge branch 'youngyangyang04:master' into master

problems/0019.删除链表的倒数第N个节点.md

@@ -204,6 +204,31 @@ fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
 }
 ```
 
+Swift：
+```swift
+func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+    if head == nil {
+        return nil
+    }
+    if n == 0 {
+        return head
+    }
+    let dummyHead = ListNode(-1, head)
+    var fast: ListNode? = dummyHead
+    var slow: ListNode? = dummyHead
+    // fast 前移 n
+    for _ in 0 ..< n {
+        fast = fast?.next
+    }
+    while fast?.next != nil {
+        fast = fast?.next
+        slow = slow?.next
+    }
+    slow?.next = slow?.next?.next
+    return dummyHead.next
+}
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)

problems/0024.两两交换链表中的节点.md

@@ -256,6 +256,27 @@ fun swapPairs(head: ListNode?): ListNode? {
 }
 ```
 
+Swift:
+```swift
+func swapPairs(_ head: ListNode?) -> ListNode? {
+    if head == nil || head?.next == nil {
+        return head
+    }
+    let dummyHead: ListNode = ListNode(-1, head)
+    var current: ListNode? = dummyHead
+    while current?.next != nil && current?.next?.next != nil {
+        let temp1 = current?.next
+        let temp2 = current?.next?.next?.next
+        
+        current?.next = current?.next?.next
+        current?.next?.next = temp1
+        current?.next?.next?.next = temp2
+        
+        current = current?.next?.next
+    }
+    return dummyHead.next
+}
+```
 
 
 -----------------------

problems/0102.二叉树的层序遍历.md

@@ -1072,6 +1072,32 @@ class Solution {
 }
 ```
 
+```java 
+//方法二：用一个max变量来保存最大值
+class Solution {
+    public List<Integer> largestValues(TreeNode root) {
+        Queue<TreeNode> queue = new LinkedList<TreeNode>();
+        List<Integer> result = new ArrayList<>();
+        if (root != null) queue.add(root);
+	
+        while(!queue.isEmpty()){
+            int size = queue.size();
+            int max = Integer.MIN_VALUE; // 初始化为最小值
+            for(int i = 0; i < size; i++){
+                TreeNode node = queue.poll();
+                max = Math.max(node.val, max);
+                if(node.left != null)
+                    queue.add(node.left);
+                if(node.right != null)
+                    queue.add(node.right);
+            }
+            result.add(max); // 取最大值放进数组
+        }
+        return result;
+    }
+}
+```
+
 go:
 
 ```GO
@@ -1597,6 +1623,43 @@ public:
 ```
 
 Java： 
+```java
+class Solution {
+
+    public int minDepth(TreeNode root){
+        if (root == null) {
+            return 0;
+        }
+
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.offer(root);
+        int depth = 0;
+
+        while (!queue.isEmpty()){
+
+            int size = queue.size();
+            depth++;
+
+            TreeNode cur = null;
+            for (int i = 0; i < size; i++) {
+                cur = queue.poll();
+
+                //如果当前节点的左右孩子都为空，直接返回最小深度
+                if (cur.left == null && cur.right == null){
+                    return depth;
+                }
+
+                if (cur.left != null) queue.offer(cur.left);
+                if (cur.right != null) queue.offer(cur.right);
+            }
+
+
+        }
+
+        return depth;
+    }
+}
+```
 
 
 Python 3：