513. Find Bottom Left Tree Value

https://leetcode.com/problems/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.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

---

算法思路：

level order

class Solution {
public:
    int findBottomLeftValue(TreeNode* root) {
        int res = 0;
        queue q;
        q.push(root);
        TreeNode* node;
        while (!q.empty()) {
            res = q.front()->val;
            for (int i = 0, n = q.size(); i < n; i++) {
                node = q.front(); q.pop();
                if (node->left) q.push(node->left);
                if (node->right) q.push(node->right);
            }
        }
        return res;
    }
};