Played with chapter two examples

chap2/chap2.go

@@ -0,0 +1,60 @@
+package main
+
+import "fmt"
+
+func searchSubsets(k, n int, subset []int) {
+	if k == n+1 {
+		// process subset
+		fmt.Println(subset)
+	} else {
+		// include k in the subset
+		subset = append(subset, k)
+		searchSubsets(k+1, n, subset)
+		subset = subset[:len(subset)-1]
+		// don’t include k in the subset
+		searchSubsets(k+1, n, subset)
+	}
+}
+
+func searchPermutations(n int, permutation []int, chosen []bool) {
+	if len(permutation) == n {
+		// process permutation
+		fmt.Println(permutation)
+	} else {
+		for i := 1; i <= n; i++ {
+			if chosen[i] {
+				continue
+			}
+			chosen[i] = true
+			permutation = append(permutation, i)
+			searchPermutations(n, permutation, chosen)
+			chosen[i] = false
+			permutation = permutation[:len(permutation)-1]
+		}
+	}
+}
+
+func searchQueens(y, n int, col, diag1, diag2 []bool) int {
+	if y == n {
+		return 1
+	}
+
+	count := 0
+	for x := 0; x < n; x++ {
+		if col[x] || diag1[x+y] || diag2[x-y+n-1] {
+			continue
+		}
+		col[x], diag1[x+y], diag2[x-y+n-1] = true, true, true
+		count += searchQueens(y+1, n, col, diag1, diag2)
+		col[x], diag1[x+y], diag2[x-y+n-1] = false, false, false
+	}
+	return count
+}
+
+func main() {
+	searchSubsets(1, 4, []int{})
+	searchPermutations(4, []int{}, make([]bool, 4+1))
+	const NB_QUEENS = 16
+	count := searchQueens(0, NB_QUEENS, make([]bool, NB_QUEENS*NB_QUEENS), make([]bool, NB_QUEENS*NB_QUEENS), make([]bool, NB_QUEENS*NB_QUEENS))
+	fmt.Println(count)
+}

go.mod

@@ -0,0 +1,3 @@
+module gitea.paas.celticinfo.fr/oabrivard/gogcp
+
+go 1.21.5