Working Zig permutations

Author: rtoal

zig/permuations.zig

@@ -1,40 +1,40 @@
 const std = @import("std");
 
-fn printPermutations(a: []u8, n: usize) void {
-    if (n <= 0) {
-        std.debug.print("{s}\n", .{a});
-    } else {
-        var i: usize = 0;
-        while (i < n) : (i += 1) {
-            printPermutations(a, n - 1);
-            const j = if (n % 2 == 0) 0 else i;
-
-            const old_a_j = a[j];
-            a[j] = a[n];
-            a[n] = old_a_j;
+fn printArray(a: []const []const u8) !void {
+    var writer = std.io.getStdOut().writer();
+    for (a, 0..) |item, i| {
+        try writer.writeAll(item);
+        if (i < a.len - 1) {
+            try writer.writeAll("\t");
         }
-        printPermutations(a, n - 1);
     }
+    try writer.writeAll("\n");
 }
 
-pub fn main() anyerror!void {
-    const args = try std.process.argsAlloc(std.heap.page_allocator);
-    defer std.process.argsFree(std.heap.page_allocator, args);
+fn printPermutations(a: [][]u8, n: usize) !void {
+    if (n == 0) {
+        try printArray(a);
+        return;
+    }
 
-    // Skip the first argument which is the program's own path
-    const start_index: usize = 1;
-    const end_index: usize = args.len;
+    try printPermutations(a, n - 1);
 
-    if (end_index >= start_index) {
-        var buffer: [100]u8 = undefined;
-        var a: []u8 = buffer[0 .. end_index - start_index];
+    var i: usize = 0;
+    while (i < n) : (i += 1) {
+        const j: usize = if (n % 2 == 0) 0 else i;
+        std.mem.swap([]const u8, &a[j], &a[n]);
+        try printPermutations(a, n - 1);
+    }
+}
 
-        // Copy the arguments to the buffer
-        for (start_index..end_index) |i| {
-            a[i - start_index] = args[i][0];
-        }
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
 
-        // Calculate and print the permutations
-        printPermutations(a, a.len - 1);
-    }
+    var args = try std.process.argsAlloc(allocator);
+    defer std.process.argsFree(allocator, args);
+    const a = try allocator.dupe([]u8, args[1..]);
+    defer allocator.free(a);
+
+    try printPermutations(a, a.len - 1);
 }