https://programmercarl.com/0968.%E7%9B%91%E6%8E%A7%E4%BA%8C%E5%8F%89%E6%A0%91.html

1.本题难点在于贪心思路的理解，对于迭代的函数的编写，而且对于二叉树的结构也要有较为完整的理解，关于思路中的几种情况的具体实现，思路考虑的还会不全，而且代码也不好写。

CPP

/**
 * 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 {
public:
    int res = 0;
    int traversal(TreeNode* node){
        
        if(node == NULL)return 2;
        int left = traversal(node->left);
        int right = traversal(node->right);

        if(left == 2 && right == 2){
            return 0;
        }
        if(left == 0 || right == 0){
            res++;
            return 1;
        }
        if(left == 1 || right == 1){
            return 2;
        }
        return -1;
    }
    int minCameraCover(TreeNode* root) {
        if(traversal(root) == 0)res++;
        
        return res;
    }
};