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Amount of Time for Binary Tree to Be Infected.cpp
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Amount of Time for Binary Tree to Be Infected.cpp
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/**
* 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:
TreeNode* createMapping(TreeNode* root, int start,unordered_map<TreeNode* , TreeNode*>&mapping){
queue<TreeNode*>q;
q.push(root);
TreeNode* res=NULL;
mapping[root]=NULL;
while(!q.empty()){
TreeNode* front=q.front();
q.pop();
if(front->val==start){
res=front;
}
if(front->left){
mapping[front->left]=front;
q.push(front->left);
}
if(front->right){
mapping[front->right]=front;
q.push(front->right);
}
}
return res;
}
int burningTree(TreeNode* res, unordered_map<TreeNode*,TreeNode*>&mapping){
unordered_map<TreeNode*,bool>visited;
visited[res]=true;
queue<TreeNode*>q;
q.push(res);
int ans=0;
while(!q.empty()){
int size=q.size();
bool flag=false;
for(int i=0;i<size;i++){
TreeNode* front=q.front();
q.pop();
if(front->left && !visited[front->left]){
q.push(front->left);
visited[front->left]=1;
flag=true;
}
if(front->right && !visited[front->right]){
q.push(front->right);
flag=true;
visited[front->right]=1;
}
if(mapping[front] && !visited[mapping[front]]){
q.push(mapping[front]);
visited[mapping[front]]=1;
flag=true;
}
}
if(flag) ans++;
}
return ans;
}
int amountOfTime(TreeNode* root, int start) {
unordered_map<TreeNode* ,TreeNode*>mapping;
TreeNode* find=createMapping(root,start,mapping);
return burningTree(find,mapping);
}
};