1 題目
給定一個二叉樹,原地將它展開爲一個單鏈表。
例如,給定二叉樹
1
/
2 5
/ \
3 4 6
將其展開爲:
1
2
3
4
5
6
2 思路
這道題我的思路比較直接,首先前序遍歷樹,然後用next指針鏈接每個節點,隨後修改原來right指針,題解的方法比較巧妙,對樹進行變形的後序遍歷,遍歷順序是右子樹->左子樹->根節點
例如,我們依次遍歷 6 5 4 3 2 1,然後每遍歷一個節點就將當前節點的右指針更新爲上一個節點,6 <- 5 <- 4 3 2 1
1
/ \
2 5
/ \ \
3 4 6
3代碼
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {void} Do not return anything, modify root in-place instead.
*/
var flatten = function(root) {
const stack = [];
let p = root;
let link = {};
let linkHead = link;
while (p || stack.length > 0) {
while (p) {
link.next = p;
link = link.next;
stack.push(p);
p = p.left;
}
p = stack.pop();
p = p.right;
}
link = linkHead.next;
while(link) {
root.right = link.next;
root.left = null;
root = root.right;
link = link.next;
}
};