Depth_First_Search

|98. Validate Binary Search Tree | [Go]({{< relref "/ChapterFour/0098.Validate-Binary-Search-Tree.md" >}})| Medium | O(n)| O(1)||
|99. Recover Binary Search Tree | [Go]({{< relref "/ChapterFour/0099.Recover-Binary-Search-Tree.md" >}})| Hard | O(n)| O(1)||
|100. Same Tree | [Go]({{< relref "/ChapterFour/0100.Same-Tree.md" >}})| Easy | O(n)| O(1)||
|101. Symmetric Tree | [Go]({{< relref "/ChapterFour/0101.Symmetric-Tree.md" >}})| Easy | O(n)| O(1)||
|104. Maximum Depth of Binary Tree  | [Go]({{< relref "/ChapterFour/0104.Maximum-Depth-of-Binary-Tree.md" >}})| Easy | O(n)| O(1)||
|108. Convert Sorted Array to Binary Search Tree | [Go]({{< relref "/ChapterFour/0108.Convert-Sorted-Array-to-Binary-Search-Tree.md" >}})| Easy | O(n)| O(1)||
|109. Convert Sorted List to Binary Search Tree | [Go]({{< relref "/ChapterFour/0109.Convert-Sorted-List-to-Binary-Search-Tree.md" >}})| Medium | O(log n)| O(n)||
|110. Balanced Binary Tree | [Go]({{< relref "/ChapterFour/0110.Balanced-Binary-Tree.md" >}})| Easy | O(n)| O(1)||
|111. Minimum Depth of Binary Tree | [Go]({{< relref "/ChapterFour/0111.Minimum-Depth-of-Binary-Tree.md" >}})| Easy | O(n)| O(1)||
|112. Path Sum | [Go]({{< relref "/ChapterFour/0112.Path-Sum.md" >}})| Easy | O(n)| O(1)||
|113. Path Sum II | [Go]({{< relref "/ChapterFour/0113.Path-Sum-II.md" >}})| Medium | O(n)| O(1)||
|114. Flatten Binary Tree to Linked List | [Go]({{< relref "/ChapterFour/0114.Flatten-Binary-Tree-to-Linked-List.md" >}})| Medium | O(n)| O(1)||
|124. Binary Tree Maximum Path Sum | [Go]({{< relref "/ChapterFour/0124.Binary-Tree-Maximum-Path-Sum.md" >}})| Hard | O(n)| O(1)||
|129. Sum Root to Leaf Numbers | [Go]({{< relref "/ChapterFour/0129.Sum-Root-to-Leaf-Numbers.md" >}})| Medium | O(n)| O(1)||
|199. Binary Tree Right Side View | [Go]({{< relref "/ChapterFour/0199.Binary-Tree-Right-Side-View.md" >}})| Medium | O(n)| O(1)||
|200. Number of Islands | [Go]({{< relref "/ChapterFour/0200.Number-of-Islands.md" >}})| Medium | O(n^2)| O(n^2)||
|207. Course Schedule | [Go]({{< relref "/ChapterFour/0207.Course-Schedule.md" >}})| Medium | O(n^2)| O(n^2)||
|210. Course Schedule II | [Go]({{< relref "/ChapterFour/0210.Course-Schedule-II.md" >}})| Medium | O(n^2)| O(n^2)||
|257. Binary Tree Paths | [Go]({{< relref "/ChapterFour/0257.Binary-Tree-Paths.md" >}})| Easy | O(n)| O(1)||
|394. Decode String | [Go]({{< relref "/ChapterFour/0394.Decode-String.md" >}})| Medium | O(n)| O(n)||
|515. Find Largest Value in Each Tree Row | [Go]({{< relref "/ChapterFour/0515.Find-Largest-Value-in-Each-Tree-Row.md" >}})| Medium | O(n)| O(n)||
|542. 01 Matrix | [Go]({{< relref "/ChapterFour/0542.01-Matrix.md" >}})| Medium | O(n)| O(1)||
|980. Unique Paths III | [Go]({{< relref "/ChapterFour/0980.Unique-Paths-III.md" >}})| Hard | O(n log n)| O(n)||