leetcode -- 114.二叉树展开为链表

https://leetcode.cn/problems/flatten-binary-tree-to-linked-list/

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题目中要求把链表展开为单链表，并且展开后的链表要跟二叉树的前序遍历顺序相同。

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     struct TreeNode *left;*     struct TreeNode *right;* };*/
void flatten(struct TreeNode* root) {struct TreeNode* cur = root;while (cur != NULL){if (cur->left != NULL) {struct TreeNode* next = cur->left;struct TreeNode* pre = next;while (pre->right != NULL) {pre = pre->right;}pre->right = cur->right;cur->left = NULL;cur->right = next;}cur = cur->right;}
}