# 662. Maximum Width of Binary Tree

Given a binary tree, write a function to get the maximum width of the given tree. The width of a tree is the maximum width among all levels. The binary tree has the same structure as a full binary tree, but some nodes are null.

The width of one level is defined as the length between the end-nodes (the leftmost and right most non-null nodes in the level, where the `null` nodes between the end-nodes are also counted into the length calculation.

Example 1:

``````Input:

1
/   \
3     2
/ \     \
5   3     9

Output: 4
Explanation: The maximum width existing in the third level with the length 4 (5,3,null,9).
``````

Example 2:

``````Input:

1
/
3
/ \
5   3

Output: 2
Explanation: The maximum width existing in the third level with the length 2 (5,3).
``````

Example 3:

``````Input:

1
/ \
3   2
/
5

Output: 2
Explanation: The maximum width existing in the second level with the length 2 (3,2).
``````

Example 4:

``````Input:

1
/ \
3   2
/     \
5       9
/         \
6           7
Output: 8
Explanation:The maximum width existing in the fourth level with the length 8 (6,null,null,null,null,null,null,7).
``````

Note: Answer will in the range of 32-bit signed integer.

``````class Solution {
public:
int widthOfBinaryTree(TreeNode* root) {
if (!root) return 0;
int res = 0;
queue<pair<TreeNode*,int>> q;
q.push({root, 1});
while (!q.empty()) {
if (q.size() == 1) q.front().second = 1;
int left = q.front().second, right = left, n = q.size();
for (int i = 0; i < n; ++i) {
auto t = q.front().first;
right = q.front().second; q.pop();
if (t->left) q.push({t->left, right * 2});
if (t->right) q.push({t->right, right * 2 + 1});
}
res = max(res, right - left + 1);
}
return res;
}
};
``````

Github 同步地址：

https://github.com/grandyang/leetcode/issues/662

https://leetcode.com/problems/maximum-width-of-binary-tree/

https://leetcode.com/problems/maximum-width-of-binary-tree/discuss/327721/cpp-bfs-solution

https://leetcode.com/problems/maximum-width-of-binary-tree/discuss/106654/javac-very-simple-dfs-solution

https://leetcode.com/problems/maximum-width-of-binary-tree/discuss/106645/cjava-bfsdfs3liner-clean-code-with-explanation

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