【leetcode】1022. Sum of Root To Leaf Binary Numbers
阿新 • • 發佈:2019-04-09
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題目如下:
Given a binary tree, each node has value
0
or1
. Each root-to-leaf path represents a binary number starting with the most significant bit. For example, if the path is0 -> 1 -> 1 -> 0 -> 1
, then this could represent01101
in binary, which is13
.For all leaves in the tree, consider the numbers represented by the path from the root to that leaf.
Return the sum of these numbers.
Example 1:
Input: [1,0,1,0,1,0,1] Output: 22 Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22
Note:
- The number of nodes in the tree is between
1
and1000
.- node.val is
0
or1
.- The answer will not exceed
2^31 - 1
.
解題思路:沒啥好說的,遞歸遍歷樹吧。
代碼如下:
# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution(object): res = 0 def recursive(self,node,path): path += str(node.val) if node.left == None andnode.right == None: self.res += int(path,2) return if node.left != None: self.recursive(node.left,path) if node.right != None: self.recursive(node.right, path) def sumRootToLeaf(self, root): """ :type root: TreeNode :rtype: int """ self.res = 0 self.recursive(root,‘‘) return self.res % (10 ** 9+ 7)
【leetcode】1022. Sum of Root To Leaf Binary Numbers