2641、二叉树的堂兄弟节点 Ⅱ——哈希表、层序遍历
使用队列进行层序遍历，sameparent记录每个节点的兄弟节点的值，同时sum用于存储当前遍历层的下一层节点总和。当遍历到下一层时，每个节点的val等于sum-兄弟节点的val。
代码语言：javascript复制/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution
{
public:
TreeNode *replaceValueInTree(TreeNode *root)
{
unordered_map<TreeNode *, int> sameparent;
queue<TreeNode *> q;
q.push(root);
sameparent[root] = 0;
int sum = root->val;
while (!q.empty())
{
int level_size = q.size();
int tmp = sum;
sum = 0;
for (size_t i = 0; i < level_size; i )
{
TreeNode *cur = q.front();
cur->val = tmp - cur->val - sameparent[cur];
if (cur->left)
{
q.push(cur->left);
sameparent[cur->left] = cur->right ? cur->right->val : 0;
sum = cur->left->val;
}
if (cur->right)
{
q.push(cur->right);
sameparent[cur->right] = cur->left ? cur->left->val : 0;
sum = cur->right->val;
}
q.pop();
}
}
return root;
}
};
