力扣1022. 从根到叶的二进制数之和（二叉树的遍历思想解决）
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int sumRootToLeaf(TreeNode root) {
traverse(root);
return res;
}
int path = 0;
int res = 0;
private void traverse(TreeNode root) {
if (root == null) {
return;
}
// Leaf root
if (root.left == null && root.right == null) {
// Add the value on the path to the res
res += path << 1 | root.val;
return;
}
// Change the value of path
path = path << 1 | root.val;
traverse(root.left);
traverse(root.right);
path = path >> 1;
}
}