[leetcode]Path Sum II

问题描写叙述：

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / 
            4   8
           /   / 
          11  13  4
         /      / 
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

public class TreeNode {
	      int val;
	      TreeNode left;
	      TreeNode right;
	      TreeNode(int x) { val = x; }
	 }
	
	public List<List<Integer>> pathSum(TreeNode root, int sum) {
		if(root == null)
    		return new ArrayList();
		
		List<List<Integer>> result = new LinkedList<List<Integer>>();
		List<Integer> list = new LinkedList<Integer>();
		
		getPathNum(root, sum,list,result);
		return result;
    }
	
	public void getPathNum(TreeNode root, int sum,List<Integer> list,List<List<Integer>> result){
    	if(root.left == null && root.right ==null){
    		if(sum == root.val){
    			List<Integer> tmp = new LinkedList<Integer>(list);
    			tmp.add(root.val);
    			result.add(tmp);
    			return;
    		}
    		else return;
    		
    	}
    	
    	list.add(root.val);
		List<Integer> ltmp = new LinkedList<Integer>(list);
		List<Integer> rtmp = new LinkedList<Integer>(list);
		
    	if(root.left !=null)
    		getPathNum(root.left, sum-root.val,ltmp,result);
    	if(root.right !=null)
    		getPathNum(root.right, sum-root.val,rtmp, result);
    	
    }