diff --git a/set1/challenge2_fixed_xor/src/main.zig b/set1/challenge2_fixed_xor/src/main.zig
index b9251ae..45ec134 100644
--- a/set1/challenge2_fixed_xor/src/main.zig
+++ b/set1/challenge2_fixed_xor/src/main.zig
@@ -1,17 +1,15 @@
 const std = @import("std");
 
-fn readHex(allocator: std.mem.Allocator, max_size: usize) ![]u8 {
-    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
-
-    var inputbuffer = std.ArrayList(u8).init(allocator);
-    defer inputbuffer.deinit();
+fn readHex(allocator: std.mem.Allocator, reader: anytype, max_size: usize) !?[]u8 {
     var resultbuffer = std.ArrayList(u8).init(allocator);
     defer resultbuffer.deinit();
 
     while (true) {
-        try stdin.readUntilDelimiterArrayList(&inputbuffer, '\n', max_size * 2);
-        try resultbuffer.resize(inputbuffer.items.len / 2);
-        _ = std.fmt.hexToBytes(resultbuffer.items, inputbuffer.items) catch {
+        const line = try reader.readUntilDelimiterOrEofAlloc(allocator, '\n', max_size * 2);
+        const hex = line orelse return null;
+        defer allocator.free(hex);
+        try resultbuffer.resize(hex.len / 2);
+        _ = std.fmt.hexToBytes(resultbuffer.items, hex) catch {
             std.log.err("not a valid hexadecimal", .{});
             continue;
         };
@@ -23,13 +21,14 @@ pub fn main() anyerror!void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
+    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
     const stdout = std.io.getStdOut().writer();
 
     while (true) {
-        const input1 = try readHex(allocator, 4096);
+        const input1 = (try readHex(allocator, stdin, 4096)) orelse break;
         defer allocator.free(input1);
 
-        const input2 = try readHex(allocator, 4096);
+        const input2 = (try readHex(allocator, stdin, 4096)) orelse break;
         defer allocator.free(input2);
 
         if (input1.len != input2.len) {
diff --git a/set1/challenge3_xor_cipher/src/main.zig b/set1/challenge3_xor_cipher/src/main.zig
index a9193a4..53ea31c 100644
--- a/set1/challenge3_xor_cipher/src/main.zig
+++ b/set1/challenge3_xor_cipher/src/main.zig
@@ -1,17 +1,15 @@
 const std = @import("std");
 
-fn readHex(allocator: std.mem.Allocator, max_size: usize) ![]u8 {
-    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
-
-    var inputbuffer = std.ArrayList(u8).init(allocator);
-    defer inputbuffer.deinit();
+fn readHex(allocator: std.mem.Allocator, reader: anytype, max_size: usize) !?[]u8 {
     var resultbuffer = std.ArrayList(u8).init(allocator);
     defer resultbuffer.deinit();
 
     while (true) {
-        try stdin.readUntilDelimiterArrayList(&inputbuffer, '\n', max_size * 2);
-        try resultbuffer.resize(inputbuffer.items.len / 2);
-        _ = std.fmt.hexToBytes(resultbuffer.items, inputbuffer.items) catch {
+        const line = try reader.readUntilDelimiterOrEofAlloc(allocator, '\n', max_size * 2);
+        const hex = line orelse return null;
+        defer allocator.free(hex);
+        try resultbuffer.resize(hex.len / 2);
+        _ = std.fmt.hexToBytes(resultbuffer.items, hex) catch {
             std.log.err("not a valid hexadecimal", .{});
             continue;
         };
@@ -42,10 +40,11 @@ pub fn main() anyerror!void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
+    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
     const stdout = std.io.getStdOut().writer();
 
     while (true) {
-        const ciphertext = try readHex(allocator, 4096);
+        const ciphertext = (try readHex(allocator, stdin, 4096)) orelse break;
         defer allocator.free(ciphertext);
 
         var plaintext = try allocator.alloc(u8, ciphertext.len);