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.

Note: A leaf is a node with no children.

Example:

Input: [1,2,3]
1
/ \
2 3
Output: 25

Explanation:

The root-to-leaf path 1->2 represents the number 12. The root-to-leaf path 1->3 represents the number 13. Therefore, sum = 12 + 13 = 25.

Example 2:

Input: [4,9,0,5,1]
4
/ \
9 0
 / \
5 1
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.

Analyze

递归解题

/**
* 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) {
const analyzeObj = { sum: 0 }
if (!root) return analyzeObj.sum
analyzeSum(root, '', analyzeObj)
return analyzeObj.sum
};
var analyzeSum = function(node, str, analyzeObj) {
if (!node) return
if (!node.left && !node.right) {
str += String(node.val)
analyzeObj.sum = analyzeObj.sum + parseInt(str, 10)
return
}
str += String(node.val)
analyzeSum(node.left, str, analyzeObj)
analyzeSum(node.right, str, analyzeObj)
}

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