1 /** 2 * Definition of TreeNode: 3 * public class TreeNode { 4 *     public int val; 5 *     public TreeNode left, right; 6 *     public TreeNode(int val) { 7 *         this.val = val; 8 *         this.left = this.right = null; 9 *     }10 * }11 */12 public class Solution {13     /*14      * @param root: the root of binary tree15      * @param target: An integer16      * @return: all valid paths17      */18     private int sum = 0;19     private List
     
      
       > result = new ArrayList
       
        
         >();20     private List
         
           path = new ArrayList
          
           ();21 public List
           
            
             > binaryTreePathSum(TreeNode root, int target) {22 // write your code here23 calculate(root, target);24 return result;25 }26 27 public void calculate(TreeNode node, int target) {28 if(node != null) {29 sum += node.val;30 path.add(node.val);31 if (sum == target && node.left == null && node.right == null) {32 List
             
               temp = new ArrayList
              
               (path); //拷贝path33 result.add(temp);34 sum -= node.val; //回溯到父节点状态35 path.remove(path.size()-1); //回溯到父节点状态36 return;37 }38 if (node.left == null && node.right == null) {39 sum -= node.val; //回溯到父节点状态40 path.remove(path.size()-1); //回溯到父节点状态41 return;42 }43 calculate(node.left, target);44 calculate(node.right, target);45 sum -= node.val; //回溯到父节点状态46 path.remove(path.size()-1); //回溯到父节点状态47 }48 }49 }
              
             
            
           
          
         
        
       
      
     

代码有点乱，有待改进。