tasks a-s

Task/N-queens-problem/Go/n-queens-problem.go

@@ -0,0 +1,61 @@
+// A fairly literal translation of the example program on the referenced
+// WP page.  Well, it happened to be the example program the day I completed
+// the task.  It seems from the WP history that there has been some churn
+// in the posted example program.  The example program of the day was in
+// Pascal and was credited to Niklaus Wirth, from his "Algorithms +
+// Data Structures = Programs."
+package main
+
+import "fmt"
+
+var (
+    i int
+    q bool
+    a [9]bool
+    b [17]bool
+    c [15]bool // offset by 7 relative to the Pascal version
+    x [9]int
+)
+
+func try(i int) {
+    for j := 1; ; j++ {
+        q = false
+        if a[j] && b[i+j] && c[i-j+7] {
+            x[i] = j
+            a[j] = false
+            b[i+j] = false
+            c[i-j+7] = false
+            if i < 8 {
+                try(i + 1)
+                if !q {
+                    a[j] = true
+                    b[i+j] = true
+                    c[i-j+7] = true
+                }
+            } else {
+                q = true
+            }
+        }
+        if q || j == 8 {
+            break
+        }
+    }
+}
+
+func main() {
+    for i := 1; i <= 8; i++ {
+        a[i] = true
+    }
+    for i := 2; i <= 16; i++ {
+        b[i] = true
+    }
+    for i := 0; i <= 14; i++ {
+        c[i] = true
+    }
+    try(1)
+    if q {
+        for i := 1; i <= 8; i++ {
+            fmt.Println(i, x[i])
+        }
+    }
+}