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binary-tree-cameras.cpp
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42 lines (40 loc) · 1.1 KB
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//https://leetcode.com/problems/binary-tree-cameras/
/**
* 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:
// first:true -> has camera
// second:true -> is being monitored
pair<bool,bool> cal(TreeNode* root,int &ans){
if(!root){
return {false,true};
}
auto l = cal(root->left,ans);
auto r = cal(root->right,ans);
bool cam = false, mon = false;
if(l.first || r.first){
mon = true;
}
if(l.second==false || r.second==false){
ans++;
cam = true;
mon = true;
}
return {cam,mon};
}
int minCameraCover(TreeNode* root) {
int ans = 0;
auto p = cal(root,ans);
if(p.second == false) ans++;
return ans;
}
};