feat: add swift implementation to lcci problem: No.16.26 (doocs#2770)

Author: klever34

lcci/16.26.Calculator/README.md

@@ -199,6 +199,47 @@ function calculate(s: string): number {
 }
 ```
 
+```swift
+class Solution {
+    func calculate(_ s: String) -> Int {
+        let n = s.count
+        var x = 0
+        var sign: Character = "+"
+        var stk = [Int]()
+        let sArray = Array(s)
+        
+        for i in 0..<n {
+            let c = sArray[i]
+            if c.isNumber {
+                x = x * 10 + Int(String(c))!
+            }
+            if i == n - 1 || (!c.isNumber && c != " ") {
+                switch sign {
+                case "+":
+                    stk.append(x)
+                case "-":
+                    stk.append(-x)
+                case "*":
+                    if let last = stk.popLast() {
+                        stk.append(last * x)
+                    }
+                case "/":
+                    if let last = stk.popLast() {
+                        stk.append(last / x)
+                    }
+                default:
+                    break
+                }
+                x = 0
+                sign = c
+            }
+        }
+        
+        return stk.reduce(0, +)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/16.26.Calculator/README_EN.md

@@ -209,6 +209,47 @@ function calculate(s: string): number {
 }
 ```
 
+```swift
+class Solution {
+    func calculate(_ s: String) -> Int {
+        let n = s.count
+        var x = 0
+        var sign: Character = "+"
+        var stk = [Int]()
+        let sArray = Array(s)
+        
+        for i in 0..<n {
+            let c = sArray[i]
+            if c.isNumber {
+                x = x * 10 + Int(String(c))!
+            }
+            if i == n - 1 || (!c.isNumber && c != " ") {
+                switch sign {
+                case "+":
+                    stk.append(x)
+                case "-":
+                    stk.append(-x)
+                case "*":
+                    if let last = stk.popLast() {
+                        stk.append(last * x)
+                    }
+                case "/":
+                    if let last = stk.popLast() {
+                        stk.append(last / x)
+                    }
+                default:
+                    break
+                }
+                x = 0
+                sign = c
+            }
+        }
+        
+        return stk.reduce(0, +)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/16.26.Calculator/Solution.swift

@@ -0,0 +1,38 @@
+class Solution {
+    func calculate(_ s: String) -> Int {
+        let n = s.count
+        var x = 0
+        var sign: Character = "+"
+        var stk = [Int]()
+        let sArray = Array(s)
+        
+        for i in 0..<n {
+            let c = sArray[i]
+            if c.isNumber {
+                x = x * 10 + Int(String(c))!
+            }
+            if i == n - 1 || (!c.isNumber && c != " ") {
+                switch sign {
+                case "+":
+                    stk.append(x)
+                case "-":
+                    stk.append(-x)
+                case "*":
+                    if let last = stk.popLast() {
+                        stk.append(last * x)
+                    }
+                case "/":
+                    if let last = stk.popLast() {
+                        stk.append(last / x)
+                    }
+                default:
+                    break
+                }
+                x = 0
+                sign = c
+            }
+        }
+        
+        return stk.reduce(0, +)
+    }
+}