3 files changed, 36 insertions, 6 deletions
diff --git a/src/2015/day4/aoc.cpp b/src/2015/day4/aoc.cpp
index 6e47928..1bb0d4e 100644
--- a/src/2015/day4/aoc.cpp
+++ b/src/2015/day4/aoc.cpp
@@ -1,3 +1,30 @@
 #include "aoc.h"
 
-namespace aoc2015 {}
+namespace aoc2015 {
+
+char* md5sum(char* s) {
+  static char md5[64] = {0};
+  uint8_t* x = md5String(s);
+  memset(md5, 0x0, 64);
+  for (auto i = 0; i < 16; i++) {
+    sprintf(md5 + i * 2, "%02x", x[i]);
+  }
+  return md5;
+}
+
+int lead_zeros(char* s) {
+  char* p = s;
+  int total = 0;
+  while (*p != '\0') {
+    if (*p == '0') {
+      total += 1;
+      p++;
+    }
+    else {
+      break;
+    }
+  }
+  return total;
+}
+
+} // namespace aoc2015
diff --git a/src/2015/day4/aoc.h b/src/2015/day4/aoc.h
index c8a6225..56d8ba3 100644
--- a/src/2015/day4/aoc.h
+++ b/src/2015/day4/aoc.h
@@ -4,4 +4,7 @@
 
 namespace aoc2015 {
 
+char* md5sum(char *);
+int lead_zeros(char*);
+
 }
diff --git a/test/test_2015.cpp b/test/test_2015.cpp
index 2aef880..a7c68a6 100644
--- a/test/test_2015.cpp
+++ b/test/test_2015.cpp
@@ -37,9 +37,9 @@ TEST_CASE("Perfectly Spherical Houses in a Vacuum", "[day3]") {
 }
 
 TEST_CASE("The Ideal Stocking Stuffer", "[day4]") {
-  char s[] = "abcdef609043";
-  uint8_t* md5 = md5String(s);
-  for (auto i = 0; i < 16; i++) {
-    printf("%x", md5[i]);
-  }
+  char s1[] = "abcdef609043";
+  char s2[] = "pqrstuv1048970";
+
+  REQUIRE(aoc2015::lead_zeros(aoc2015::md5sum(s1)) >= 5);
+  REQUIRE(aoc2015::lead_zeros(aoc2015::md5sum(s2)) >= 5);
 }