Commit 282659b

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feat: add swift implementation to lcof2 problem: No.040 (doocs#3050)

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Original file line number	Diff line number	Diff line change
`@@ -254,6 +254,57 @@ func largestRectangleArea(heights []int) int {`
`254`	`254`	`}`
`255`	`255`	```
`256`	`256`
	`257`	`+#### Swift`
	`258`	`+`
	`259`	+```swift
	`260`	`+class Solution {`
	`261`	`+ func maximalRectangle(_ matrix: [String]) -> Int {`
	`262`	`+ guard let firstRow = matrix.first else {`
	`263`	`+ return 0`
	`264`	`+ }`
	`265`	`+`
	`266`	`+ let n = firstRow.count`
	`267`	`+ var heights = [Int](repeating: 0, count: n)`
	`268`	`+ var ans = 0`
	`269`	`+`
	`270`	`+ for row in matrix {`
	`271`	`+ for (j, char) in row.enumerated() {`
	`272`	`+ if char == "1" {`
	`273`	`+ heights[j] += 1`
	`274`	`+ } else {`
	`275`	`+ heights[j] = 0`
	`276`	`+ }`
	`277`	`+ }`
	`278`	`+ ans = max(ans, largestRectangleArea(heights))`
	`279`	`+ }`
	`280`	`+`
	`281`	`+ return ans`
	`282`	`+ }`
	`283`	`+`
	`284`	`+ private func largestRectangleArea(_ heights: [Int]) -> Int {`
	`285`	`+ var res = 0`
	`286`	`+ let n = heights.count`
	`287`	`+ var stack = [Int]()`
	`288`	`+ var left = [Int](repeating: -1, count: n)`
	`289`	`+ var right = [Int](repeating: n, count: n)`
	`290`	`+`
	`291`	`+ for i in 0..<n {`
	`292`	`+ while !stack.isEmpty && heights[stack.last!] >= heights[i] {`
	`293`	`+ right[stack.removeLast()] = i`
	`294`	`+ }`
	`295`	`+ left[i] = stack.isEmpty ? -1 : stack.last!`
	`296`	`+ stack.append(i)`
	`297`	`+ }`
	`298`	`+`
	`299`	`+ for i in 0..<n {`
	`300`	`+ res = max(res, heights[i] * (right[i] - left[i] - 1))`
	`301`	`+ }`
	`302`	`+`
	`303`	`+ return res`
	`304`	`+ }`
	`305`	`+}`
	`306`	+```
	`307`	`+`
`257`	`308`	`<!-- tabs:end -->`
`258`	`309`
`259`	`310`	`<!-- solution:end -->`

Lines changed: 46 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,46 @@`
	`1`	`+class Solution {`
	`2`	`+ func maximalRectangle(_ matrix: [String]) -> Int {`
	`3`	`+ guard let firstRow = matrix.first else {`
	`4`	`+ return 0`
	`5`	`+ }`
	`6`	`+`
	`7`	`+ let n = firstRow.count`
	`8`	`+ var heights = [Int](repeating: 0, count: n)`
	`9`	`+ var ans = 0`
	`10`	`+`
	`11`	`+ for row in matrix {`
	`12`	`+ for (j, char) in row.enumerated() {`
	`13`	`+ if char == "1" {`
	`14`	`+ heights[j] += 1`
	`15`	`+ } else {`
	`16`	`+ heights[j] = 0`
	`17`	`+ }`
	`18`	`+ }`
	`19`	`+ ans = max(ans, largestRectangleArea(heights))`
	`20`	`+ }`
	`21`	`+`
	`22`	`+ return ans`
	`23`	`+ }`
	`24`	`+`
	`25`	`+ private func largestRectangleArea(_ heights: [Int]) -> Int {`
	`26`	`+ var res = 0`
	`27`	`+ let n = heights.count`
	`28`	`+ var stack = [Int]()`
	`29`	`+ var left = [Int](repeating: -1, count: n)`
	`30`	`+ var right = [Int](repeating: n, count: n)`
	`31`	`+`
	`32`	`+ for i in 0..<n {`
	`33`	`+ while !stack.isEmpty && heights[stack.last!] >= heights[i] {`
	`34`	`+ right[stack.removeLast()] = i`
	`35`	`+ }`
	`36`	`+ left[i] = stack.isEmpty ? -1 : stack.last!`
	`37`	`+ stack.append(i)`
	`38`	`+ }`
	`39`	`+`
	`40`	`+ for i in 0..<n {`
	`41`	`+ res = max(res, heights[i] * (right[i] - left[i] - 1))`
	`42`	`+ }`
	`43`	`+`
	`44`	`+ return res`
	`45`	`+ }`
	`46`	`+}`

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