feat: add solutions to lc problem: No.0662

No.0662.Maximum Width of Binary Tree

Author: yanglbme

solution/0600-0699/0662.Maximum Width of Binary Tree/README.md

@@ -77,22 +77,160 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
+BFS 层序遍历。
+
 <!-- tabs:start -->
 
 ### **Python3**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def widthOfBinaryTree(self, root: TreeNode) -> int:
+        q = deque([(root, 1)])
+        ans = 0
+        while q:
+            n = len(q)
+            ans = max(ans, q[-1][1] - q[0][1] + 1)
+            for _ in range(n):
+                node, j = q.popleft()
+                if node.left:
+                    q.append((node.left, 2 * j))
+                if node.right:
+                    q.append((node.right, 2 * j + 1))
+        return ans
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    public int widthOfBinaryTree(TreeNode root) {
+        Deque<Pair<TreeNode, Integer>> q = new ArrayDeque<>();
+        q.offerLast(new Pair<>(root, 1));
+        int ans = 0;
+        while (!q.isEmpty()) {
+            ans = Math.max(ans, q.peekLast().getValue() - q.peekFirst().getValue() + 1);
+            for (int i = 0, n = q.size(); i < n; ++i) {
+                Pair<TreeNode, Integer> node = q.pollFirst();
+                if (node.getKey().left != null) {
+                    q.offerLast(new Pair<>(node.getKey().left, node.getValue() * 2));
+                }
+                if (node.getKey().right != null) {
+                    q.offerLast(new Pair<>(node.getKey().right, node.getValue() * 2 + 1));
+                }
+            }
+        }
+        return ans;
+    }
+}
+```
+
+### **C++**
+
+`start * 2` 表示下一层的起点，防止索引溢出。计算下一层左右子树索引时，减去 `start * 2`，可以防止溢出。
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int widthOfBinaryTree(TreeNode* root) {
+        queue<pair<TreeNode*, int>> q;
+        q.emplace(root, 1);
+        int ans = 0;
+        while (!q.empty())
+        {
+            ans = max(ans, q.back().second - q.front().second + 1);
+            int start = q.front().second;
+            for (int i = 0, n = q.size(); i < n; ++i)
+            {
+                auto node = q.front();
+                q.pop();
+                if (node.first->left != nullptr) q.emplace(node.first->left, node.second * 2 - start * 2);
+                if (node.first->right != nullptr) q.emplace(node.first->right, node.second * 2 + 1 - start * 2);
+            }
+        }
+        return ans;
+    }
+};
+```
 
+### **Go**
+
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+type Node struct {
+	node *TreeNode
+	idx  int
+}
+
+func widthOfBinaryTree(root *TreeNode) int {
+	q := []Node{{root, 1}}
+	ans := 0
+	for len(q) > 0 {
+		ans = max(ans, q[len(q)-1].idx-q[0].idx+1)
+		n := len(q)
+		for i := 0; i < n; i++ {
+			node := q[0]
+			q = q[1:]
+			if node.node.Left != nil {
+				q = append(q, Node{node.node.Left, node.idx * 2})
+			}
+			if node.node.Right != nil {
+				q = append(q, Node{node.node.Right, node.idx*2 + 1})
+			}
+		}
+	}
+	return ans
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
 ```
 
 ### **...**