feat: add swift implementation to lcci problem: No.08.12 (#2704)

Author: klever34

lcci/08.12.Eight Queens/README.md

@@ -246,6 +246,49 @@ public class Solution {
 }
 ```
 
+```swift
+class Solution {
+    private var ans: [[String]] = []
+    private var col: [Int] = Array(repeating: 0, count: 0)
+    private var dg: [Int] = Array(repeating: 0, count: 0)
+    private var udg: [Int] = Array(repeating: 0, count: 0)
+    private var g: [[String]] = Array(repeating: Array(repeating: ".", count: 0), count: 0)
+    private var n: Int = 0
+
+    func solveNQueens(_ n: Int) -> [[String]] {
+        self.n = n
+        col = Array(repeating: 0, count: n)
+        dg = Array(repeating: 0, count: n * 2)
+        udg = Array(repeating: 0, count: n * 2)
+        g = Array(repeating: Array(repeating: ".", count: n), count: n)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        guard i < n else {
+            let t = g.map { $0.joined() }
+            ans.append(t)
+            return
+        }
+        for j in 0..<n {
+            if col[j] + dg[i + j] + udg[n - i + j] == 0 {
+                g[i][j] = "Q"
+                col[j] = 1
+                dg[i + j] = 1
+                udg[n - i + j] = 1
+                dfs(i + 1)
+                col[j] = 0
+                dg[i + j] = 0
+                udg[n - i + j] = 0
+                g[i][j] = "."
+            }
+        }
+    }
+
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.12.Eight Queens/README_EN.md

@@ -261,6 +261,49 @@ public class Solution {
 }
 ```
 
+```swift
+class Solution {
+    private var ans: [[String]] = []
+    private var col: [Int] = Array(repeating: 0, count: 0)
+    private var dg: [Int] = Array(repeating: 0, count: 0)
+    private var udg: [Int] = Array(repeating: 0, count: 0)
+    private var g: [[String]] = Array(repeating: Array(repeating: ".", count: 0), count: 0)
+    private var n: Int = 0
+
+    func solveNQueens(_ n: Int) -> [[String]] {
+        self.n = n
+        col = Array(repeating: 0, count: n)
+        dg = Array(repeating: 0, count: n * 2)
+        udg = Array(repeating: 0, count: n * 2)
+        g = Array(repeating: Array(repeating: ".", count: n), count: n)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        guard i < n else {
+            let t = g.map { $0.joined() }
+            ans.append(t)
+            return
+        }
+        for j in 0..<n {
+            if col[j] + dg[i + j] + udg[n - i + j] == 0 {
+                g[i][j] = "Q"
+                col[j] = 1
+                dg[i + j] = 1
+                udg[n - i + j] = 1
+                dfs(i + 1)
+                col[j] = 0
+                dg[i + j] = 0
+                udg[n - i + j] = 0
+                g[i][j] = "."
+            }
+        }
+    }
+
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.12.Eight Queens/Solution.swift

@@ -0,0 +1,40 @@
+class Solution {
+    private var ans: [[String]] = []
+    private var col: [Int] = Array(repeating: 0, count: 0)
+    private var dg: [Int] = Array(repeating: 0, count: 0)
+    private var udg: [Int] = Array(repeating: 0, count: 0)
+    private var g: [[String]] = Array(repeating: Array(repeating: ".", count: 0), count: 0)
+    private var n: Int = 0
+
+    func solveNQueens(_ n: Int) -> [[String]] {
+        self.n = n
+        col = Array(repeating: 0, count: n)
+        dg = Array(repeating: 0, count: n * 2)
+        udg = Array(repeating: 0, count: n * 2)
+        g = Array(repeating: Array(repeating: ".", count: n), count: n)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        guard i < n else {
+            let t = g.map { $0.joined() }
+            ans.append(t)
+            return
+        }
+        for j in 0..<n {
+            if col[j] + dg[i + j] + udg[n - i + j] == 0 {
+                g[i][j] = "Q"
+                col[j] = 1
+                dg[i + j] = 1
+                udg[n - i + j] = 1
+                dfs(i + 1)
+                col[j] = 0
+                dg[i + j] = 0
+                udg[n - i + j] = 0
+                g[i][j] = "."
+            }
+        }
+    }
+
+}