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;
}
}