diff --git a/set1/challenge4_detect_xor/src/main.zig b/set1/challenge4_detect_xor/src/main.zig
index 5540cd0..a7dd342 100644
--- a/set1/challenge4_detect_xor/src/main.zig
+++ b/set1/challenge4_detect_xor/src/main.zig
@@ -43,8 +43,8 @@ pub fn main() anyerror!void {
     const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
     const stdout = std.io.getStdOut().writer();
 
-    var bestplaintext = try allocator.alloc(u8, 0);
-    defer allocator.free(bestplaintext);
+    var bestplaintext = std.ArrayList(u8).init(allocator);
+    defer bestplaintext.deinit();
     var bestscore: u32 = 0;
 
     while (true) {
@@ -58,9 +58,8 @@ pub fn main() anyerror!void {
             decrypt(plaintext, ciphertext, key);
             const s = score(plaintext);
             if (s > bestscore) {
-                allocator.free(bestplaintext);
-                bestplaintext = try allocator.alloc(u8, plaintext.len);
-                std.mem.copy(u8, bestplaintext, plaintext);
+                try bestplaintext.resize(plaintext.len);
+                std.mem.copy(u8, bestplaintext.items, plaintext);
                 bestscore = s;
             }
             key +%= 1;
@@ -70,5 +69,5 @@ pub fn main() anyerror!void {
         }
     }
 
-    try stdout.print("{s}\n", .{bestplaintext});
+    try stdout.print("{s}\n", .{bestplaintext.items});
 }