515. Find Largest Value in Each Tree Row-LeetCode

// Just Use map Conatiner To Hold The Value Of Every Level

class Solution {
public:
    int mx=0;
    map<int,vector<int>>m;
    void pre(TreeNode* root,int lev)
    {
        mx=max(lev,mx);
        m[lev].push_back(root->val);
        if(root->left!=NULL)
        {
            pre(root->left,lev+1);
        }
        if(root->right!=NULL)
        {
             pre(root->right,lev+1);
        }
    }
    vector<int> largestValues(TreeNode* root) {
        vector<int>p;
        if(root==NULL)
        {
            return p;
        }
        
        int ans=0;
        pre(root,0);
        for(int i=0;i<=mx;i++)
        {
            ans=INT_MIN;
            for(int j=0;j<m[i].size();j++)
            {
                ans=max(ans,m[i][j]);
            }
            p.push_back(ans);
        }
        return p;
    }
};