sum-root-to-leaf-numbers
题目描述
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.
思路
- 根据题意，我们可以根据先序遍历的顺序一边遍历一边计算
- 注意：设置两个值temp和sum，每次进入结点的时候temp加一次，每次从这个节点出来的时候temp减去这个节点的值，遍历到叶子节点的时候要对sum进行一次计算
代码
/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public int sumNumbers(TreeNode root) { int[] data = {0, 0}; // {temp, sum} if (root != null) { getSum(root, data); } return data[1]; } public void getSum(TreeNode root, int[] data) { data[0] *= 10; data[0] += root.val; if (root.left == null && root.right == null) { data[1] += data[0]; data[0] -= root.val; data[0] /= 10; return; } if (root.left != null) { getSum(root.left, data); } if (root.right != null) { getSum(root.right, data); } data[0] -= root.val; data[0] /= 10; } }