Data commit

Task/N-queens-problem/Swift/n-queens-problem.swift

@@ -0,0 +1,56 @@
+	let maxn = 31
+
+	func nq(n: Int) -> Int {
+	    var cols = Array(repeating: 0, count: maxn)
+	    var diagl = Array(repeating: 0, count: maxn)
+	    var diagr = Array(repeating: 0, count: maxn)
+	    var posibs = Array(repeating: 0, count: maxn)
+	    var num = 0
+	    for q0 in 0...n-3 {
+		for q1 in q0+2...n-1 {
+		    let bit0: Int = 1<<q0
+		    let bit1: Int = 1<<q1
+		    var d: Int = 0
+		    cols[0] = bit0 | bit1 | (-1<<n)
+		    diagl[0] = (bit0<<1|bit1)<<1
+		    diagr[0] = (bit0>>1|bit1)>>1
+
+		    var posib: Int = ~(cols[0] | diagl[0] | diagr[0])
+
+		    while (d >= 0) {
+			while(posib != 0) {
+			    let bit: Int = posib & -posib
+			    let ncols: Int = cols[d] | bit
+			    let ndiagl: Int = (diagl[d] | bit) << 1;
+			    let ndiagr: Int = (diagr[d] | bit) >> 1;
+			    let nposib: Int = ~(ncols | ndiagl | ndiagr);
+			    posib^=bit
+			    num += (ncols == -1 ? 1 : 0)
+			    if (nposib != 0){
+				if(posib != 0) {
+				    posibs[d] = posib
+				    d += 1
+				}
+				cols[d] = ncols
+				diagl[d] = ndiagl
+				diagr[d] = ndiagr
+				posib = nposib
+			    }
+			}
+			d -= 1
+			posib = d<0 ? n : posibs[d]
+
+		    }
+		}
+
+	    }
+	    return num*2
+	}
+	if(CommandLine.arguments.count == 2) {
+
+	    let board_size: Int = Int(CommandLine.arguments[1])!
+	    print ("Number of solutions for board size \(board_size) is: \(nq(n:board_size))")
+
+	} else {
+	    print("Usage: 8q <n>")
+	}