LeetCode；515. Find Largest Value in Each Tree Row

You need to find the largest value in each row of a binary tree.

Example:

Input: 

          1
         / \
        3   2
       / \   \  
      5   3   9 

Output: [1, 3, 9]
      

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AC：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<int> res;
public: 
    vector<int> largestValues(TreeNode* root) {
        if(root==NULL)
            return res;
        findlarge(root,0);
        return res;
    }
    
    void findlarge(TreeNode* root,int level)
    {
        if(root==NULL)
            return;
        if(res.size()<level+1)
            res.push_back(root->val);
        else {
            if (res[level] < root->val) {
                res[level] = root->val;
            }
        }
        findlarge(root->left, level+1);
        findlarge(root->right, level+1);
    }
};