diff --git a/CMakeLists.txt b/CMakeLists.txt
index e0eb1b6..9bfece6 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,7 +40,7 @@ set(TARGETS day-01 day-02) # Add the other days as you please.
 
 list(LENGTH TARGETS NUM_TARGETS)
 
-set(LIBGUF_IMPLS ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_alloc_libc_impl.c ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_str_impl.c  ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_init_impl.c )
+set(LIBGUF_IMPLS ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_alloc_libc_impl.c ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_str_impl.c  ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/guf_init_impl.c ${CMAKE_CURRENT_SOURCE_DIR}/libguf_impls/dict_impl.c)
 
 foreach(current_target IN LISTS TARGETS)
     add_executable(${current_target} ${current_target}/${current_target}.c ${LIBGUF_IMPLS})
diff --git a/day-02/day-02.c b/day-02/day-02.c
index b6d1581..791c37b 100644
--- a/day-02/day-02.c
+++ b/day-02/day-02.c
@@ -3,10 +3,12 @@
 #include "guf_str.h"
 #include "guf_math.h"
 
+#include "libguf_impls/dict_impl.h"
+
 /*
     - Part 1: 54234399924 (Example: 1227775554)
 
-    - Part 2: (Example: )
+    - Part 2: 70187097315 (Example: 4174379265)
 */
 
 guf_allocator g_allocator; 
@@ -56,6 +58,10 @@ uint64_t solution(guf_str_view input, bool part_two)
     guf_str_init_empty(&start_str, &g_allocator);
     guf_str_init_empty(&end_str, &g_allocator);
 
+      dict_u64_bool seen_invalid_ids; 
+        dict_u64_bool_init(&seen_invalid_ids, &g_allocator); 
+
+
     while (read_id_range(&input, &range)) {
         guf_str_append_u64(&start_str, range.start); 
         guf_str_append_u64(&end_str, range.end);
@@ -63,30 +69,44 @@ uint64_t solution(guf_str_view input, bool part_two)
         const int n_digits_end = (int)guf_str_len(&end_str);
 
         // Generate all pairs of one, two, three, ... digits (without leading zeroes)
-        for (int half_n_digits = 1; half_n_digits <= 10; ++half_n_digits) {
+        for (int half_n_digits = 1; half_n_digits <= 20; ++half_n_digits) {
             if (half_n_digits * 2 > n_digits_end) {
                 break;
-            } else if (half_n_digits * 2 < n_digits_start) {
-                continue;
-            }
+            } 
 
-            const uint64_t min_half = pow_10(half_n_digits - 1); 
+            uint64_t min_half = pow_10(half_n_digits - 1); 
             const uint64_t max_half = pow_10(half_n_digits) - 1;
 
             for (uint64_t cur_half = min_half; cur_half <= max_half; ++cur_half) {
-                uint64_t id = cur_half * pow_10(half_n_digits) + cur_half;
-                if (id > range.end) {
-                    break;
-                } else if (id >= range.start) {
-                    invalid_id_sum += id;
+                if (!part_two) { // Part 1:
+                    uint64_t id = cur_half * pow_10(half_n_digits) + cur_half;
+                    if (id > range.end) {
+                        break;
+                    } else if (id >= range.start) {
+                        invalid_id_sum += id;
+                    }
+                } else { // Part 2:
+                    uint64_t id = cur_half; 
+                    for (int reps = 0; reps < 20; ++reps) {
+                         id = id * pow_10(half_n_digits) + cur_half;
+                        if (id > range.end) {
+                            break;
+                        } else if (id >= range.start) {
+                            if (!dict_u64_bool_contains_val_arg(&seen_invalid_ids, id)) {
+                                invalid_id_sum += id;
+                                dict_u64_bool_insert_val_arg(&seen_invalid_ids, id, true, GUF_CPY_VALUE, GUF_CPY_VALUE);
+                            }
+                        }
+                    }
                 }
             }
         }
-
         guf_str_substr(&start_str, 0, 0);
         guf_str_substr(&end_str, 0, 0);
     }
 
+    dict_u64_bool_free(&seen_invalid_ids, NULL);
+
    return invalid_id_sum;
 }
 
@@ -108,8 +128,8 @@ int main(int argc, const char **argv)
     const uint64_t p1_result = solution(guf_str_view_from_str(&input_str), false);
     printf("Part 1: %" PRIu64 "\n", p1_result);
     
-    // const uint64_t p2_result = solution(guf_str_view_from_str(&input_str), true);
-    // printf("Part 2: %" PRIu64 "\n", p2_result);
+    const uint64_t p2_result = solution(guf_str_view_from_str(&input_str), true);
+    printf("Part 2: %" PRIu64 "\n", p2_result);
 
     guf_str_free(&input_str, NULL);
 
diff --git a/libguf_impls/dict_impl.c b/libguf_impls/dict_impl.c
new file mode 100644
index 0000000..79e6ee8
--- /dev/null
+++ b/libguf_impls/dict_impl.c
@@ -0,0 +1,10 @@
+#include "dict_impl.h"
+
+#define GUF_DICT_KEY_T uint64_t
+#define GUF_DICT_KEY_HASH uint64_hash
+#define GUF_DICT_KEY_T_EQ uint64_eq
+#define GUF_DICT_VAL_T bool
+#define GUF_DICT_VAL_T_IS_INTEGRAL_TYPE
+#define GUF_DICT_NAME dict_u64_bool
+#define GUF_DICT_IMPL
+#include "guf_dict.h"
diff --git a/libguf_impls/dict_impl.h b/libguf_impls/dict_impl.h
new file mode 100644
index 0000000..8e24fbc
--- /dev/null
+++ b/libguf_impls/dict_impl.h
@@ -0,0 +1,22 @@
+#ifndef GUF_DICT_IMPL_H
+#define GUF_DICT_IMPL_H
+#include "guf_hash.h"
+
+static inline guf_hash_size_t uint64_hash(const uint64_t *a)
+{
+    return guf_hash(a, sizeof(uint64_t), GUF_HASH_INIT); // TODO: byte order...
+}
+static inline bool uint64_eq(const uint64_t *a, const uint64_t *b)
+{
+    return *a == *b;
+}
+#define GUF_DICT_KEY_T uint64_t
+#define GUF_DICT_KEY_HASH uint64_hash
+#define GUF_DICT_KEY_T_EQ uint64_eq
+#define GUF_DICT_VAL_T bool
+#define GUF_DICT_VAL_T_IS_INTEGRAL_TYPE
+#define GUF_DICT_NAME dict_u64_bool
+#include "guf_dict.h"
+
+
+#endif
\ No newline at end of file