Leetcode 257 Binary Tree Paths java

问题：
Given a binary tree, return all root-to-leaf paths.
Note: A leaf is a node with no children.

Example:
Input:

   1
 /   \
2     3
 \
  5

Output: [“1->2->5”, “1->3”]

Explanation: All root-to-leaf paths are: 1->2->5, 1->3

解答

public class L257 {
	class TreeNode{
		int val;
		TreeNode left;
		TreeNode right;
		
		public TreeNode(int val) {
			this.val = val;
		}
	}
	
	List<String> resultList = new ArrayList<String>();
	
	public List<String> binaryTreePaths(TreeNode root) {
		deepSearch(root, new StringBuilder());
		return resultList;
	}
	//用一个递归就odek
	public void deepSearch(TreeNode root, StringBuilder stringBuilder) {
		if(root == null) 
			return ;
		if(root.left == null && root.right == null) {
			stringBuilder.append(root.val);
			resultList.add(stringBuilder.toString());
			return ;
		}
		
		stringBuilder.append(root.val + "->");
		
		if(root.left != null)
			deepSearch(root.left, new StringBuilder(stringBuilder.toString()));
		if(root.right != null)
			deepSearch(root.right, new StringBuilder(stringBuilder.toString()));
		
	}
}