Java二叉树路径和代码示例

  1
 / \
 2 4
 / \
 2 3

[
 [1, 2, 2],
 [1, 4]
]

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *  public int val;
 *  public TreeNode left, right;
 *  public TreeNode(int val) {
 *   this.val = val;
 *   this.left = this.right = null;
 *  }
 * }
 */
public class Solution {
	/**
  * @param root the root of binary tree
  * @param target an integer
  * @return all valid paths
  */
	public List<List<Integer>> binaryTreePathSum(TreeNode root, int target) {
		// Write your code here
		return dfs(root,new ArrayList<Integer>(),0,new ArrayList<List<Integer>>(),target);
	}
	public List<List<Integer>> dfs(TreeNode root,List<Integer> node, int sum, List<List<Integer>> paths,int target)
	 {
		if(root==null)
		  {
			return new ArrayList<List<Integer>>();
		}
		List<List<Integer>> path=new ArrayList<List<Integer>>();
		if(root.left!=null)
		  {
			List<Integer> nodes=new ArrayList<Integer>();
			if(node!=null)
			  {
				nodes.addAll(node);
			}
			nodes.add(root.val);
			List<List<Integer>> temp=dfs(root.left,nodes,sum+root.val,paths,target);
			if(temp!=null)
			   {
				path.addAll(temp);
			}
		}
		if(root.right!=null)
		  {
			List<Integer> nodes=new ArrayList<Integer>();
			if(node!=null)
			  {
				nodes.addAll(node);
			}
			nodes.add(root.val);
			List<List<Integer>> temp=dfs(root.right,nodes,sum+root.val,paths,target);
			if(temp!=null)
			   {
				path.addAll(temp);
			}
		}
		if(root.left==null&&root.right==null)
		  {
			List<Integer> nodes=new ArrayList<Integer>();
			if(node!=null)
			  {
				nodes.addAll(node);
			}
			nodes.add(root.val);
			if(sum+root.val==target)
			   {
				path.add(nodes);
			} else{
				path=new ArrayList<List<Integer>>();
			}
		}
		return path;
	}
}