LeetCode 501 二叉搜索树中的众数

• 分析
  中序遍历，顺便使用几个变量进行信息记录
• 代码

/**
 * 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) {}
 * };
 */
class Solution{
private:
    int pre;
    int num;
    int max;    
public:
    Solution():max(-1), num(0), pre(INT_MIN){}
    vector<int> findMode(TreeNode* root){
        vector<int> vec;
        traverse(root, vec);
        return vec;
    }

    void traverse(TreeNode* root, vector<int>& vec){
        if(root == nullptr) return;

        traverse(root -> left, vec);        
        if(pre == INT_MIN){
            pre = root -> val;
            num = 1;
            vec.push_back(pre);
            max = 1;
              
        }else{
            if(root -> val == pre){
                num++;
                if(num > max){
                    vec.clear();
                    vec.push_back(pre);
                    max = num;
                }else if(num == max){
                    vec.push_back(pre);
                }
            }else if(root -> val != pre){
                pre = root -> val;
                num = 1;
                if(num > max){
                    vec.clear();
                    vec.push_back(pre);
                    max = num;
                }else if(num == max){
                    vec.push_back(pre);
                }
            }
        }
        traverse(root -> right, vec);
    }
};