1 | Given a binary tree |
使用queue层序遍历1
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29/**
* Definition for binary tree with next pointer.
* struct TreeLinkNode {
* int val;
* TreeLinkNode *left, *right, *next;
* TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
* };
*/
class Solution {
public:
void connect(TreeLinkNode *root) {
queue<TreeLinkNode*> q;
if (!root) return;
q.push(root);
while (!q.empty()) {
size_t sz = q.size();
TreeLinkNode *last = NULL;
for (size_t i = 0; i < sz; i++) {
auto tmp = q.front(); q.pop();
if (last) last->next = tmp;
last = tmp;
if (tmp->left) q.push(tmp->left);
if (tmp->right) q.push(tmp->right);
}
last->next = NULL;
}
}
};
使用O(1)空间,我们维护两层关系,上一层已经被设置好所有next指针,下一层保存开头节点后结尾节点,然后按序尝试更新尾节点,最后到达下一层
1 | /** |