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Description
/**
* 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 {
public:
int res = 0;
int dfs(TreeNode* root){
if(root == nullptr) return 2;
auto left = dfs(root->left);
auto right = dfs(root->right);
if(left == 0 || right == 0){
res++;
return 1;
}
return left == 1 || right == 1 ? 2 : 0;
}
int minCameraCover(TreeNode* root) {
return (dfs(root) < 1 ? 1 : 0) + res;
}
};