Medium：Find Bottom Left Tree Value

513. Find Bottom Left Tree Value

题目：

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.

代码如下：

class Solution {
public:
    int findLeftMostNode(TreeNode* root) {
        queue<TreeNode*> q;
        queue<int> level;

        q.push(root);
        level.push(0);

        int m=0;
        while(q.size()){
            TreeNode *r = q.front(); q.pop();
            int l = level.front(); level.pop();
            if(r->left) {
                q.push(r->left);
                level.push(l+1);
            }
            if(r->right){
                q.push(r->right);
                level.push(l+1);
            }
            if(l > m){
                m = l;
                root = r;
            }
        }
        return root->val;
    }
};

• 运用BFS算法；
• 与上一道题解法类似。