【树】Sum Root to Leaf Numbers

题目：

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：

利用栈进行深度优先遍历。

/**
* Definition for a binary tree node.
* function TreeNode(val) {
*     this.val = val;
*     this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @return {number}
*/
var sumNumbers = function(root) {
if(root==null){
return 0;
}

function Node(treeNode,sum){
this.treeNode=treeNode;
this.sum=sum;
}

var res=0,stack=[];
var n=new Node(root,root.val);
stack.push(n);

while(stack.length!=0){
var p=stack.pop();
if(p.treeNode.left==null&&p.treeNode.right==null){
res+=p.sum;
}else{
if(p.treeNode.left!=null){
stack.push(new Node(p.treeNode.left,p.sum*10+p.treeNode.left.val))
}
if(p.treeNode.right!=null){
stack.push(new Node(p.treeNode.right,p.sum*10+p.treeNode.right.val))
}
}
}

return res;
};