Commit 51fef98

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feat: add swift implementation to lcci problem: No.04.05 (doocs#2657)

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Lines changed: 41 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -291,6 +291,47 @@ public class Solution {`
`291`	`291`	`}`
`292`	`292`	```
`293`	`293`
	`294`	+```swift
	`295`	`+/* class TreeNode {`
	`296`	`+* var val: Int`
	`297`	`+* var left: TreeNode?`
	`298`	`+* var right: TreeNode?`
	`299`	`+*`
	`300`	`+* init(_ val: Int) {`
	`301`	`+* self.val = val`
	`302`	`+* self.left = nil`
	`303`	`+* self.right = nil`
	`304`	`+* }`
	`305`	`+* }`
	`306`	`+*/`
	`307`	`+`
	`308`	`+class Solution {`
	`309`	`+ private var prev: TreeNode?`
	`310`	`+`
	`311`	`+ func isValidBST(_ root: TreeNode?) -> Bool {`
	`312`	`+ return dfs(root)`
	`313`	`+ }`
	`314`	`+`
	`315`	`+ private func dfs(_ root: TreeNode?) -> Bool {`
	`316`	`+ guard let root = root else {`
	`317`	`+ return true`
	`318`	`+ }`
	`319`	`+`
	`320`	`+ if !dfs(root.left) {`
	`321`	`+ return false`
	`322`	`+ }`
	`323`	`+`
	`324`	`+ if let prev = prev, prev.val >= root.val {`
	`325`	`+ return false`
	`326`	`+ }`
	`327`	`+`
	`328`	`+ prev = root`
	`329`	`+`
	`330`	`+ return dfs(root.right)`
	`331`	`+ }`
	`332`	`+}`
	`333`	+```
	`334`	`+`
`294`	`335`	`<!-- tabs:end -->`
`295`	`336`
`296`	`337`	`<!-- end -->`

Lines changed: 41 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -328,6 +328,47 @@ public class Solution {`
`328`	`328`	`}`
`329`	`329`	```
`330`	`330`
	`331`	+```swift
	`332`	`+/* class TreeNode {`
	`333`	`+* var val: Int`
	`334`	`+* var left: TreeNode?`
	`335`	`+* var right: TreeNode?`
	`336`	`+*`
	`337`	`+* init(_ val: Int) {`
	`338`	`+* self.val = val`
	`339`	`+* self.left = nil`
	`340`	`+* self.right = nil`
	`341`	`+* }`
	`342`	`+* }`
	`343`	`+*/`
	`344`	`+`
	`345`	`+class Solution {`
	`346`	`+ private var prev: TreeNode?`
	`347`	`+`
	`348`	`+ func isValidBST(_ root: TreeNode?) -> Bool {`
	`349`	`+ return dfs(root)`
	`350`	`+ }`
	`351`	`+`
	`352`	`+ private func dfs(_ root: TreeNode?) -> Bool {`
	`353`	`+ guard let root = root else {`
	`354`	`+ return true`
	`355`	`+ }`
	`356`	`+`
	`357`	`+ if !dfs(root.left) {`
	`358`	`+ return false`
	`359`	`+ }`
	`360`	`+`
	`361`	`+ if let prev = prev, prev.val >= root.val {`
	`362`	`+ return false`
	`363`	`+ }`
	`364`	`+`
	`365`	`+ prev = root`
	`366`	`+`
	`367`	`+ return dfs(root.right)`
	`368`	`+ }`
	`369`	`+}`
	`370`	+```
	`371`	`+`
`331`	`372`	`<!-- tabs:end -->`
`332`	`373`
`333`	`374`	`<!-- end -->`

Lines changed: 38 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,38 @@`
	`1`	`+/* class TreeNode {`
	`2`	`+* var val: Int`
	`3`	`+* var left: TreeNode?`
	`4`	`+* var right: TreeNode?`
	`5`	`+*`
	`6`	`+* init(_ val: Int) {`
	`7`	`+* self.val = val`
	`8`	`+* self.left = nil`
	`9`	`+* self.right = nil`
	`10`	`+* }`
	`11`	`+* }`
	`12`	`+*/`
	`13`	`+`
	`14`	`+class Solution {`
	`15`	`+ private var prev: TreeNode?`
	`16`	`+`
	`17`	`+ func isValidBST(_ root: TreeNode?) -> Bool {`
	`18`	`+ return dfs(root)`
	`19`	`+ }`
	`20`	`+`
	`21`	`+ private func dfs(_ root: TreeNode?) -> Bool {`
	`22`	`+ guard let root = root else {`
	`23`	`+ return true`
	`24`	`+ }`
	`25`	`+`
	`26`	`+ if !dfs(root.left) {`
	`27`	`+ return false`
	`28`	`+ }`
	`29`	`+`
	`30`	`+ if let prev = prev, prev.val >= root.val {`
	`31`	`+ return false`
	`32`	`+ }`
	`33`	`+`
	`34`	`+ prev = root`
	`35`	`+`
	`36`	`+ return dfs(root.right)`
	`37`	`+ }`
	`38`	`+}`

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