tasks a-s

Task/N-queens-problem/Java/n-queens-problem.java

@@ -0,0 +1,48 @@
+public class NQueens {
+
+  private static int[] b = new int[8];
+  private static int s = 0;
+
+  static boolean unsafe(int y) {
+    int x = b[y];
+    for (int i = 1; i <= y; i++) {
+      int t = b[y - i];
+      if (t == x ||
+          t == x - i ||
+          t == x + i) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  public static void putboard() {
+    System.out.println("\n\nSolution " + (++s));
+    for (int y = 0; y < 8; y++) {
+      for (int x = 0; x < 8; x++) {
+        System.out.print((b[y] == x) ? "|Q" : "|_");
+      }
+      System.out.println("|");
+    }
+  }
+
+  public static void main(String[] args) {
+    int y = 0;
+    b[0] = -1;
+    while (y >= 0) {
+      do {
+        b[y]++;
+      } while ((b[y] < 8) && unsafe(y));
+      if (b[y] < 8) {
+        if (y < 7) {
+          b[++y] = -1;
+        } else {
+          putboard();
+        }
+      } else {
+        y--;
+      }
+    }
+  }
+}