[LeetCode]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   3

The 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

.

思路：采用深度优先搜索的方法，每搜索到一个点，就更新自身的值

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int sumNumbers(TreeNode root) {
if (root == null) return 0;
int res = 0;
Stack<TreeNode> s = new Stack<TreeNode>();
TreeNode temp = new TreeNode(0);
s.push(root);
while(s.isEmpty() == false) {
temp = s.pop();
if(temp.left == null && temp.right == null) {
res = res + temp.val;
}
if(temp.right != null) {
temp.right.val = temp.right.val + temp.val*10;
s.push(temp.right);
}
if(temp.left != null) {
temp.left.val = temp.left.val + temp.val*10;
s.push(temp.left);
}
}
return res;
}
}