Maximum Width of Binary Tree (M)
題目
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.
題意
找到給定二叉樹的最大寬度，每層的寬度定義為每層第一個非空結點到最后一個非空結點的距離，
思路
層序遍歷，建兩個佇列，一個記錄結點，一個記錄對應結點在當前層的序號，
代碼實作
Java
class Solution {
public int widthOfBinaryTree(TreeNode root) {
Queue<TreeNode> nodes = new LinkedList<>();
Queue<Integer> order = new LinkedList<>();
int max = 0;
if (root != null) {
nodes.offer(root);
order.offer(0);
}
while (!nodes.isEmpty()) {
int size = nodes.size();
int start = 0, end = 0;
for (int i = 0; i < size; i++) {
TreeNode cur = nodes.poll();
int num = order.poll();
start = i == 0 ? num : start;
end = i == size - 1 ? num : end;
if (cur.left != null) {
nodes.offer(cur.left);
order.offer(num * 2);
}
if (cur.right != null) {
nodes.offer(cur.right);
order.offer(num * 2 + 1);
}
}
max = Math.max(max, end - start + 1);
}
return max;
}
}
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