diff --git a/exercises/ex05/find_track_oo.c b/exercises/ex05/find_track_oo.c
index d039a6d3..3cf219c3 100644
--- a/exercises/ex05/find_track_oo.c
+++ b/exercises/ex05/find_track_oo.c
@@ -20,7 +20,9 @@ char tracks[][80] = {
 };
 
 
-typedef regex_t Regex;
+typedef struct {
+    regex_t inner_struct[1];
+} Regex;
 
 
 /* Returns a new Regex that matches the given pattern.
@@ -30,27 +32,50 @@ typedef regex_t Regex;
 * returns: new Regex
 */
 Regex *make_regex(char *pattern, int flags) {
-    // FILL THIS IN!
-    return NULL;
+    regex_t regex;
+    int ret;
+
+    ret = regcomp(&regex, pattern, REG_EXTENDED | REG_NOSUB);
+    if (ret) {
+        fprintf(stderr, "Could not compile regex\n");
+        exit(1);
+    }
+
+    Regex *r = malloc(sizeof(Regex));
+    r->inner_struct[0] = regex;
+
+    return r;
 }
 
 /* Checks whether a regex matches a string.
 *
-* regex: Regex pointer
+* regex: Regex
 * s: string
 * returns: 1 if there's a match, 0 otherwise
 */
 int regex_match(Regex *regex, char *s) {
-    // FILL THIS IN!
-    return 0;
+    int ret;
+    char msgbuf[100];
+
+    ret = regexec(&(regex->inner_struct[0]), s, 0, NULL, 0);
+    if (!ret) {
+        // printf("Track %i: '%s'\n", i, tracks[i]);
+        return 1;
+    } else if (ret == REG_NOMATCH) {
+        return 0;
+    } else {
+        regerror(ret, &(regex->inner_struct[0]), msgbuf, sizeof(msgbuf));
+        fprintf(stderr, "Regex match failed: %s\n", msgbuf);
+        exit(1);
+    }
 }
 
 /* Frees a Regex.
 *
-* regex: Regex pointer
+* regex: Regex
 */
 void regex_free(Regex *regex) {
-    // FILL THIS IN!
+    regfree(&(regex->inner_struct[0]));
 }
 
 
diff --git a/exercises/ex05/rand.c b/exercises/ex05/rand.c
index 2235cd40..1ae04180 100644
--- a/exercises/ex05/rand.c
+++ b/exercises/ex05/rand.c
@@ -5,6 +5,8 @@ License: MIT License https://opensource.org/licenses/MIT
 */
 
 #include <stdlib.h>
+#include "rand.h"
+#include <inttypes.h>
 
 // generate a random float using the algorithm described
 // at http://allendowney.com/research/rand
@@ -78,7 +80,37 @@ float my_random_float2()
 // compute a random double using my algorithm
 double my_random_double()
 {
-    // TODO: fill this in
+    int mant;
+    int exp = 2047;
+    int mask = 1;
+    uint64_t x;
+
+    union {
+        double d;
+        int i;
+    } b;
+
+    // generate random bits until we see the first set bit
+    while (1) {
+        x = rand();
+        if (x == 0) {
+            exp -= 63;
+        } else {
+            break;
+        }
+    }
+
+    // find the location of the first set bit and compute the exponent
+    while (x & mask) {
+        mask <<= 1;
+        exp--;
+    }
+
+    // use the remaining bit as the mantissa
+    mant = x >> 12;
+    b.i = (exp << 52) | mant;
+
+    return b.d;
 }
 
 // return a constant (this is a dummy function for time trials)
@@ -114,7 +146,7 @@ float random_float()
 
 
 // generate a random double using the standard algorithm
-float random_double()
+double random_double()
 {
     int x;
     double f;
diff --git a/exercises/ex05/time_rand.c b/exercises/ex05/time_rand.c
index edbb1b3f..6a7deb9a 100644
--- a/exercises/ex05/time_rand.c
+++ b/exercises/ex05/time_rand.c
@@ -32,7 +32,6 @@ double get_seconds() {
 }
 
 /* Compute the total time used by a function.
-
 iters: number of times to call the function
 func: function to call
 */
@@ -52,8 +51,24 @@ double time_func(int iters, float(*func)())
     return t1 - t0;
 }
 
+double time_func_double(int iters, double(*func)())
+{
+    int i;
+    double d;
+    double t0, t1;
+
+    srandom(time(NULL));
+
+    t0 = get_seconds();
+    for (i=0; i<iters; i++) {
+        d = func();
+    }
+    t1 = get_seconds();
+    return t1 - t0;
+}
+
 
-main(int argc, char *argv[])
+int main(int argc, char *argv[])
 {
     double time;
     int iters = 100000000;
@@ -74,6 +89,11 @@ main(int argc, char *argv[])
     time = time_func(iters, my_random_float2);
     printf("%f ms \t my_random_float2\n", time);
 
-    time = time_func(iters, random_float);
-    printf("%f ms \t random_float\n", time);
+    printf("\n");
+
+    time = time_func_double(iters, random_double);
+    printf("%f ms \t random_double\n", time);
+
+    time = time_func_double(iters, my_random_double);
+    printf("%f ms \t my_random_double\n", time);
 }