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+# 2641. Cousins in Binary Tree II
+from collections import Counter
+
+"""
+given the 'root' of a binary tree, replace the value of each node in the tree
+with the sum of all its cousins' values. two nodes of a binary tree are
+cousins if they have the same depth with different paths. return 'root' of
+the modified tree. note that the depth of a nodie is a number of edges in the
+path from the root node to it.
+"""
+
+
+# Definition for a binary tree node.
+class TreeNode(object):
+ def __init__(self, val=0, left=None, right=None):
+ self.val = val
+ self.left = left
+ self.right = right
+
+
+class Solution(object):
+ def replaceValueInTree(self, root):
+ """
+ :type root: Optional[TreeNode]
+ :rtype: Optional[TreeNode]
+ """
+ sum = Counter()
+
+ def dfs1(r, l):
+ if not r:
+ return
+ sum[l] += r.val
+ dfs1(r.left, l + 1)
+ dfs1(r.right, l + 1)
+
+ dfs1(root, 0)
+
+ def dfs2(r, l, curr):
+ cousin_sum = (
+ sum[l + 1]
+ - (r.left.val if r.left else 0)
+ - (r.right.val if r.right else 0)
+ )
+ if r.left:
+ curr.left = TreeNode(cousin_sum)
+ dfs2(r.left, l + 1, curr.left)
+ if r.right:
+ curr.right = TreeNode(cousin_sum)
+ dfs2(r.right, l + 1, curr.right)
+ return curr
+
+ return dfs2(root, 0, TreeNode(0))
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.replaceValueInTree(root=[5, 4, 9, 1, 10, None, 7]))
+ print(obj.replaceValueInTree(root=[3, 1, 2]))