https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list/
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前序遍历
class Solution { public void flatten(TreeNode root) { List<TreeNode> list = new ArrayList<>(); preorderTraversal(root,list); for(int i=1;i<list.size();i++){ TreeNode prev = list.get(i-1),cur=list.get(i); prev.left = null; prev.right = cur; } } public void preorderTraversal(TreeNode root,List<TreeNode> list){ if(root!=null){ list.add(root); preorderTraversal(root.left,list); preorderTraversal(root.right,list); } } }
