7575
7676<!-- 这里可写通用的实现逻辑 -->
7777
78+ “BFS 层次遍历”实现。
79+
7880<!-- tabs:start -->
7981
8082### ** Python3**
8183
8284<!-- 这里可写当前语言的特殊实现逻辑 -->
8385
8486``` python
85-
87+ # Definition for a binary tree node.
88+ # class TreeNode:
89+ # def __init__(self, val=0, left=None, right=None):
90+ # self.val = val
91+ # self.left = left
92+ # self.right = right
93+ class Solution :
94+ def largestValues (self root : TreeNode) -> List[int ]:
95+ if root is None :
96+ return []
97+ q = collections.deque([root])
98+ res = []
99+ while q:
100+ n = len (q)
101+ t = float (' -inf'
102+ for _ in range (n):
103+ node = q.popleft()
104+ t = max (t, node.val)
105+ if node.left:
106+ q.append(node.left)
107+ if node.right:
108+ q.append(node.right)
109+ res.append(t)
110+ return res
86111```
87112
88113### ** Java**
89114
90115<!-- 这里可写当前语言的特殊实现逻辑 -->
91116
92117``` java
93-
118+ /**
119+ * Definition for a binary tree node.
120+ * public class TreeNode {
121+ * int val;
122+ * TreeNode left;
123+ * TreeNode right;
124+ * TreeNode() {}
125+ * TreeNode(int val) { this.val = val; }
126+ * TreeNode(int val, TreeNode left, TreeNode right) {
127+ * this.val = val;
128+ * this.left = left;
129+ * this.right = right;
130+ * }
131+ * }
132+ */
133+ class Solution {
134+ public List<Integer > largestValues (TreeNode root ) {
135+ if (root == null ) {
136+ return Collections . emptyList();
137+ }
138+ Deque<TreeNode > q = new ArrayDeque<> ();
139+ q. offer(root);
140+ List<Integer > res = new ArrayList<> ();
141+ while (! q. isEmpty()) {
142+ int t = Integer . MIN_VALUE
143+ for (int i = 0 , n = q. size(); i < n; ++ i) {
144+ TreeNode node = q. poll();
145+ t = Math . max(t, node. val);
146+ if (node. left != null ) {
147+ q. offer(node. left);
148+ }
149+ if (node. right != null ) {
150+ q. offer(node. right);
151+ }
152+ }
153+ res. add(t);
154+ }
155+ return res;
156+ }
157+ }
94158```
95159
96160### ** C++**
@@ -100,32 +164,32 @@ class Solution {
100164public:
101165 vector<int > largestValues(TreeNode* root) {
102166 vector<int > res;
103- if( !root )
167+ if ( !root)
104168 {
105169 return res;
106170 }
107171
108- deque<TreeNode* > deq;
172+ deque<TreeNode * > deq;
109173 deq.push_back(root);
110- while( !deq.empty())
174+ while ( !deq.empty())
111175 {
112176 int size = deq.size();
113177 int maxnum = INT_MIN;
114178 for (int i = 0; i < size; i++)
115179 {
116- TreeNode* ptr = deq.front();
180+ TreeNode * ptr = deq.front();
117181 deq.pop_front();
118- if(maxnum < ptr->val)
182+ if (maxnum < ptr->val)
119183 {
120184 maxnum = ptr->val;
121185 }
122186
123- if (ptr->left)
187+ if (ptr->left)
124188 {
125189 deq.push_back(ptr->left);
126190 }
127191
128- if(ptr->right)
192+ if (ptr->right)
129193 {
130194 deq.push_back(ptr->right);
131195 }
0 commit comments