标签：style blog http 使用 io strong for ar art
OJ: https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node/
Given a binary tree
struct TreeLinkNode {
TreeLinkNode *left;
TreeLinkNode *right;
TreeLinkNode *next;
}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
Initially, all next pointers are set to NULL.
Note:
For example, Given the following perfect binary tree,
1
/ 2 3
/ \ / 4 5 6 7
After calling your function, the tree should look like:
1 -> NULL
/ 2 -> 3 -> NULL
/ \ / 4->5->6->7 -> NULL
思想： 常量空间要求，决定了不能使用递归。满二叉树，简单循环，每次修改一层即可。
/**
* 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) {
TreeLinkNode *p = root;
while(p && p->left) {
p->left->next = p->right;
TreeLinkNode *pre = p, *cur = p->next;
while(cur) {
pre->right->next = cur->left;
cur->left->next = cur->right;
pre = cur;
cur = cur->next;
}
p = p->left;
}
}
};
OJ: https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/
Follow up for problem "Populating Next Right Pointers in Each Node".
What if the given tree could be any binary tree? Would your previous solution still work?
Note:
For example, Given the following binary tree,
1
/ 2 3
/ \ 4 5 7
After calling your function, the tree should look like:
1 -> NULL
/ 2 -> 3 -> NULL
/ \ 4-> 5 -> 7 -> NULL
思想同上： 但是下一层最开始结点和连接过程中链表的第一个结点不易确定，所以需要设定两个变量来保存。
/**
* 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) {
TreeLinkNode *curListNode, *startNode, *curNode;
startNode = root;
while(startNode) {
curNode = startNode;
startNode = curListNode = NULL;
while(curNode) {
if(curNode->left) {
if(startNode == NULL) startNode = curNode->left;
if(curListNode == NULL) curListNode = curNode->left;
else { curListNode->next = curNode->left; curListNode = curListNode->next; }
}
if(curNode->right) {
if(startNode == NULL) startNode =curNode->right;
if(curListNode == NULL) curListNode = curNode->right;
else { curListNode->next = curNode->right; curListNode = curListNode->next; }
}
curNode = curNode->next;
}
}
}
};
29. Populating Next Right Pointers in Each Node && Populating Next Right Pointers in Each Node II
标签：style blog http 使用 io strong for ar art
原文地址：http://www.cnblogs.com/liyangguang1988/p/3939512.html
