概述：
左耳朵耗子專欄《左耳聽風》 用戶自發每週完成一個ARTS：
1.Algorithm：每週至少做一個 leetcode 的算法題
2.Review：閱讀並點評至少一篇英文技術文章
3.Tip：學習至少一個技術技巧
4.Share：分享一篇有觀點和思考的技術文章
Algorithm
題目概述：
Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.
An example is the root-to-leaf path1->2->3which represents the number123.
Find the total sum of all root-to-leaf numbers.
For example,
1
/ \
2 3
The root-to-leaf path1->2represents the number12.
The root-to-leaf path1->3represents the number13.
Return the sum = 12 + 13 =25.
代碼：
/**
* Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.
* <p>
* An example is the root-to-leaf path1->2->3which represents the number123.
* <p>
* Find the total sum of all root-to-leaf numbers.
* <p>
* For example,
* The root-to-leaf path1->2represents the number12.
* The root-to-leaf path1->3represents the number13.
* <p>
* Return the sum = 12 + 13 =25.
*
* @author idea
* @data 2019/7/14
*/
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) {
val = x;
}
}
public class TotalDemo {
private StringBuilder stb = new StringBuilder();
public Integer sum=new Integer(0);
public int sumNumbers(TreeNode root) {
StringBuilder stb = new StringBuilder();
findLeafNodeParent(root, stb);
return sum;
}
/**
* 查詢葉子節點
*
* @return
*/
public void findLeafNodeParent(TreeNode root, StringBuilder current) {
if (root == null) {
return;
}
current.append(root.val);
if (isLeaf(root)) {
sum += Integer.parseInt(current + "");
}
findLeafNodeParent(root.left, current);
findLeafNodeParent(root.right, current);
current.deleteCharAt(current.length() - 1);
}
/**
* 判斷是否是葉子節點
*
* @param root
* @return
*/
public boolean isLeaf(TreeNode root) {
return root.left == null && root.right == null;
}
public static void main(String[] args) {
TreeNode t1 = new TreeNode(1);
TreeNode t2 = new TreeNode(2);
TreeNode t3 = new TreeNode(3);
TreeNode t4 = new TreeNode(4);
TreeNode t5 = new TreeNode(5);
TreeNode t6 = new TreeNode(6);
t1.left = t2;
t1.right = t3;
t2.left = t4;
t2.right = t5;
t5.left = t6;
TotalDemo td = new TotalDemo();
Integer sum = td.sumNumbers(t1);
System.out.println(sum);
}
}