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Given the root
of a binary tree, each node has a value from 0
to 25
representing the letters 'a'
to 'z'
: a value of 0
represents 'a'
, a value of 1
represents 'b'
, and so on.
Find the lexicographically smallest string that starts at a leaf of this tree and ends at the root.
(As a reminder, any shorter prefix of a string is lexicographically smaller: for example, "ab"
is lexicographically smaller than "aba"
. A leaf of a node is a node that has no children.)
Example 1:
Input: [0,1,2,3,4,3,4]
Output: "dba"
Example 2:
Input: [25,1,3,1,3,0,2]
Output: "adz"
Example 3:
Input: [2,2,1,null,1,0,null,0]
Output: "abc"
Note:
- The number of nodes in the given tree will be between
1
and 8500
.
- Each node in the tree will have a value between
0
and 25
.
[Tree]
[Depth-first Search]
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