Create 0051-n-queens.swift

Author: drxlx

swift/0051-n-queens.swift

@@ -0,0 +1,37 @@
+class Solution {
+    func solveNQueens(_ n: Int) -> [[String]] {
+        var res = [[String]]()
+        var col = Set<Int>()
+        var posDiag = Set<Int>()
+        var negDiag = Set<Int>()
+        var cur = Array(repeating: Array(repeating: ".", count: n), count: n)
+
+        func dfs(_ r: Int) {
+            if r == n {
+                let copy = cur.map { $0.joined() }
+                print(copy)
+                res.append(copy)
+                return
+            }
+
+            for c in 0..<n {
+                if col.contains(c) || posDiag.contains(r + c) || negDiag.contains(r - c) {
+                    continue
+                }
+                col.insert(c)
+                posDiag.insert(r + c)
+                negDiag.insert(r - c)
+                cur[r][c] = "Q"
+                dfs(r + 1)
+                col.remove(c)
+                posDiag.remove(r + c)
+                negDiag.remove(r - c)
+                cur[r][c] = "."
+            }
+        }
+
+        dfs(0)
+
+        return res
+    }
+}