Data update

Task/Permutations-by-swapping/Zig/permutations-by-swapping.zig

@@ -0,0 +1,50 @@
+const std = @import("std");
+
+// Generic function to generate permutations
+fn generate(comptime T: type, a: []T, output: fn ([]const T, i64) void) void {
+    const n = a.len;
+    var c = std.heap.page_allocator.alloc(usize, n) catch unreachable;
+    defer std.heap.page_allocator.free(c);
+
+    @memset(c, 0);
+
+    var i: usize = 1;
+    var sign: i64 = 1;
+    output(a, sign);
+
+    while (i < n) {
+        if (c[i] < i) {
+            if ((i & 1) == 0) {
+                std.mem.swap(T, &a[0], &a[i]);
+            } else {
+                std.mem.swap(T, &a[c[i]], &a[i]);
+            }
+            sign = -sign;
+            output(a, sign);
+            c[i] += 1;
+            i = 1;
+        } else {
+            c[i] = 0;
+            i += 1;
+        }
+    }
+}
+
+// Function to print permutation and its sign
+fn printPermutation(comptime T: type) fn ([]const T, i64) void {
+    return struct {
+        fn inner(a: []const T, sign: i64) void {
+            std.debug.print("{any} {}\n", .{ a, sign });
+        }
+    }.inner;
+}
+
+pub fn main() !void {
+    std.debug.print("Permutations and signs for three items:\n", .{});
+    var a = [_]i32{ 0, 1, 2 };
+    generate(i32, &a, printPermutation(i32));
+
+    std.debug.print("\nPermutations and signs for four items:\n", .{});
+    var b = [_]i32{ 0, 1, 2, 3 };
+    generate(i32, &b, printPermutation(i32));
+}