leetcode-java-129. Sum Root to Leaf Numbers

/*Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the number 123.Find the total sum of all root-to-leaf numbers.For example,    1   / \  2   3The root-to-leaf path 1->2 represents the number 12. The root-to-leaf path 1->3 represents the number 13.Return the sum = 12 + 13 = 25. */ /**  * Definition for a binary tree node.  * public class TreeNode {  *     int val;  *     TreeNode left;  *     TreeNode right;  *     TreeNode(int x) { val = x; }  * }  */ /*思路：其实就是找到所有的路径(递归)，进行处理，然后把所有路径得到的数字相加,可以参考题目257  */  public class Solution {      public int sumNumbers(TreeNode root) {          List<Integer> list = new LinkedList<Integer>();          if(root == null){              return 0;          }          int sum = 0;          findPaths(list,sum,root);          for(Integer i:list) {              sum += i;          }          return sum;      }      public void findPaths(List<Integer> list,Integer sum,TreeNode root) {          if(root == null) {              return;          }          if(root.left == null && root.right == null) {              list.add(sum*10 + root.val);              return;          }          findPaths(list,sum*10+root.val,root.left);          findPaths(list,sum*10+root.val,root.right);      }  }