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.
递归法
复杂度
时间 O(N) 空间 O(N) 递归栈空间
思路
简单的二叉树遍历,遍历时将自身的数值加入子节点。比如节点A的值是1,其左子节点的值是2,则将左子节点变为12。一旦遍历到叶子节点便将该叶子结点的值加入结果中。
代码
public class Solution {
int sum = 0;
public int sumNumbers(TreeNode root) {
if(root != null) getSum(root);
return sum;
}
private void getSum(TreeNode n){
if(n.left == null && n.right == null){
sum += n.val;
}
if(n.left != null){
n.left.val += n.val * 10;
getSum(n.left);
}
if(n.right != null){
n.right.val += n.val * 10;
getSum(n.right);
}
}
}
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