how to make a function from using global var to not using it
2024-08-26 03:05:17
let say, we want to find the bottom left node in a tree.
one way to do it is using global vars:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution
{ public int findBottomLeftValue(TreeNode root)
{
find(root, 0);
return d_bottomLeft.val;
} private int d_bottomDepth = -1;
private TreeNode d_bottomLeft = null;
private void find(TreeNode node, int depth)
{
if (node == null) return;
if (depth >= d_bottomDepth)
{
d_bottomDepth = depth;
d_bottomLeft = node;
} find(node.right, depth + 1);
find(node.left , depth + 1);
}
}
to avoid using global vars, we can write it in this way:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution
{
public int findBottomLeftValue(TreeNode root)
{
Result result = new Result();
find(root, 0, result);
return result.d_bottomLeft.val;
} private void find(TreeNode node, int depth, Result result)
{
if (node == null) return;
if (depth >= result.d_bottomDepth)
{
result.d_bottomDepth = depth;
result.d_bottomLeft = node;
}
find(node.right, depth + 1, result);
find(node.left , depth + 1, result);
} private class Result
{
public int d_bottomDepth = -1;
public TreeNode d_bottomLeft = null;
}
}
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