vault backup: 2022-07-07 08:37:25

CS notes/pages/Leetcode Search-In-a-Binary-Tree.md

@@ -63,6 +63,10 @@ Output: []
 > [!summary]
 > This is a #DFS or #BFS problem. We search values in the tree.
 
+In DFS, I use preorder, since the root value will be check first, making it quicker if data appear on shallow trees more.
+
+In BFS, I don't have use for loop inside while loop, since we don't have to consider levels.
+
 ### Solution
 
 DFS
@@ -142,5 +146,41 @@ public:
 
 BFS
 ```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:
+  TreeNode *searchBST(TreeNode *root, int val) {
+    // BFS
+    queue<TreeNode *> pending;
+    pending.push(root);
 
+    TreeNode *ptr;
+    while (!pending.empty()) {
+      ptr = pending.front();
+      pending.pop();
+
+      if (ptr->val == val) {
+        return ptr;
+      }
+
+      if (ptr->left)
+        pending.push(ptr->left);
+      if (ptr->right)
+        pending.push(ptr->right);
+    }
+
+    return nullptr;
+  }
+};
 ```