Leetcode：513. Find Bottom Left Tree Value

Given a binary tree, find the leftmost value in the last row of the tree.

Example 1:
Input:

2

/ \
1 3

Output:
1
Example 2:
Input:

    1
   / \
  2   3
 /   / \
4   5   6
   /
  7

Output:
7
Note: You may assume the tree (i.e., the given root node) is not NULL.

注意：！！！
是求 最後一層最左邊的元素的val

//Definition for a binary tree node.
    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) { val = x; }
    }

    public class Solution {
        int ans=0, h=0;
        public int findBottomLeftValue(TreeNode root) {
            findBottomLeftValue(root, 1);
            return ans;
        }
        public void findBottomLeftValue(TreeNode root, int depth) {
            //初始化的時候h=0 此時爲根結點 h爲1
            if (h<depth) {ans=root.val;h=depth;}
            /**
             * 遞歸 直到Find The Ans
             */
            //如果root的左孩子不爲空 遞歸 根結點變爲左孩子 深度加1
            if (root.left!=null) findBottomLeftValue(root.left, depth+1);
            if (root.right!=null) findBottomLeftValue(root.right, depth+1);
        }
    }