|218. The Skyline Problem | [Go]({{< relref "/ChapterFour/0218.The-Skyline-Problem.md" >}})| Hard | O(n log n)| O(n)|❤️|
|307. Range Sum Query - Mutable | [Go]({{< relref "/ChapterFour/0307.Range-Sum-Query---Mutable.md" >}})| Hard | O(1)| O(n)||
|315. Count of Smaller Numbers After Self | [Go]({{< relref "/ChapterFour/0315.Count-of-Smaller-Numbers-After-Self.md" >}})| Hard | O(n log n)| O(n)||
|327. Count of Range Sum | [Go]({{< relref "/ChapterFour/0327.Count-of-Range-Sum.md" >}})| Hard | O(n log n)| O(n)|❤️|
|493. Reverse Pairs | [Go]({{< relref "/ChapterFour/0493.Reverse-Pairs.md" >}})| Hard | O(n log n)| O(n)||
|699. Falling Squares | [Go]({{< relref "/ChapterFour/0699.Falling-Squares.md" >}})| Hard | O(n log n)| O(n)|❤️|
|715. Range Module | [Go]({{< relref "/ChapterFour/0715.Range-Module.md" >}})| Hard | O(log n)| O(n)|❤️|
|732. My Calendar III  | [Go]({{< relref "/ChapterFour/0732.My-Calendar-III.md" >}})| Hard | O(log n)| O(n)|❤️|
|850. Rectangle Area II  | [Go]({{< relref "/ChapterFour/0850.Rectangle-Area-II.md" >}})| Hard | O(n log n)| O(n)|❤️|
|1157. Online Majority Element In Subarray | [Go]({{< relref "/ChapterFour/1157.Online-Majority-Element-In-Subarray.md" >}})| Hard | O(log n)| O(n)|❤️|