diff --git a/cscoin-heap64.c b/cscoin-heap64.c
new file mode 100644
index 0000000..76d8c7e
--- /dev/null
+++ b/cscoin-heap64.c
@@ -0,0 +1,86 @@
+#include "cscoin-heap64.h"
+
+CSCoinHeap64 *
+cscoin_heap64_new (guint64 *heap, gsize heap_len, GCompareFunc cmp)
+{
+    CSCoinHeap64 *self;
+
+    self = g_malloc (sizeof (CSCoinHeap64));
+
+    cscoin_heap64_init (self, heap, heap_len, cmp);
+
+    return self;
+}
+
+void
+cscoin_heap64_init (CSCoinHeap64 *self, guint64 *heap, gsize heap_len, GCompareFunc cmp)
+{
+    g_return_if_fail (self != NULL);
+
+    self->heap     = heap;
+    self->heap_len = heap_len;
+    self->cmp      = cmp;
+
+    gint i;
+    for (i = 0; i < self->heap_len; i++)
+    {
+        self->heap[i] = CSCOIN_HEAP64_NULL;
+    }
+}
+
+gboolean
+cscoin_heap64_push (CSCoinHeap64 *self, guint64 val)
+{
+    gint i;
+    guint64 tmp;
+
+    g_return_val_if_fail (self != NULL, FALSE);
+    g_return_val_if_fail (val != CSCOIN_HEAP64_NULL, FALSE);
+
+    i = 0;
+    while (self->heap[i++] != CSCOIN_HEAP64_NULL);
+
+    self->heap[i - 1] = val;
+
+    /* heapify */
+    while (i > 1)
+    {
+        /* swap parent & child */
+        if (self->cmp (self->heap + ((i - 1) / 2), self->heap + i) < 0)
+        {
+            tmp = self->heap[(i - 1) / 2];
+            self->heap[(i - 1) / 2] = tmp;
+            self->heap[i] = tmp;
+        }
+        i--;
+    }
+
+    return TRUE;
+}
+
+guint64
+cscoin_heap64_pop (CSCoinHeap64 *self)
+{
+    gint i;
+    guint64 ret;
+
+    ret = self->heap[0];
+
+    for (i = 0; i < self->heap_len && self->heap[i] != CSCOIN_HEAP64_NULL;)
+    {
+        if (self->cmp (self->heap + 2 * i + 1, self->heap + 2 * i + 2) < 0)
+        {
+            // raise left
+            self->heap[i] = self->heap[2 * i + 1];
+            i = (2 * i) + 1;
+        }
+        else
+        {
+            // raise right
+            self->heap[i] = self->heap[2 * i + 2];
+            i = (2 * i) + 2;
+        }
+    }
+
+    return ret;
+}
diff --git a/cscoin-heap64.h b/cscoin-heap64.h
new file mode 100644
index 0000000..960bdd3
--- /dev/null
+++ b/cscoin-heap64.h
@@ -0,0 +1,31 @@
+#ifndef __CSCOIN_HEAP64_H__
+#define __CSCOIN_HEAP64_H__
+
+#include <glib.h>
+
+/* random sentinel (don't use this value explicitly) */
+#define CSCOIN_HEAP64_NULL G_GUINT64_CONSTANT (12839182022384)
+
+typedef struct _CSCoinHeap64 CSCoinHeap64;
+
+struct _CSCoinHeap64
+{
+    guint64      *heap;
+    gsize         heap_len;
+    GCompareFunc  cmp;
+};
+
+CSCoinHeap64 * cscoin_heap64_new     (guint64      *heap,
+                                      gsize         heap_len,
+                                      GCompareFunc  cmp);
+void           cscoin_heap64_free    (CSCoinHeap64 *self);
+void           cscoin_heap64_init    (CSCoinHeap64 *self,
+                                      guint64      *heap,
+                                      gsize         heap_len,
+                                      GCompareFunc  cmp);
+gboolean       cscoin_heap64_push    (CSCoinHeap64 *self, guint64 val);
+guint64        cscoin_heap64_pop     (CSCoinHeap64 *self);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (CSCoinHeap64, cscoin_heap64_free);
+
+#endif /* __CSCOIN_HEAP64_H__ */
diff --git a/cscoin-solver.c b/cscoin-solver.c
index 9829e66..c7ffe75 100644
--- a/cscoin-solver.c
+++ b/cscoin-solver.c
@@ -1,5 +1,6 @@
 #include "cscoin-solver.h"
 #include "cscoin-mt64.h"
+#include "cscoin-heap64.h"
 
 #include <omp.h>
 #include <openssl/sha.h>
@@ -63,11 +64,13 @@ cscoin_solve_challenge (gint           challenge_id,
             guint16 prefix;
         } checksum_digest;
         guint64 numbers[nb_elements];
+        CSCoinHeap64 numbers_heap;
         guint nonce;
         gchar nonce_str[32];
         gint i;
 
         cscoin_mt64_init (&mt64);
+        cscoin_heap64_init (&numbers_heap, numbers, nb_elements, guint64cmp_asc);
 
         /* OpenMP partitionning */
         guint nonce_from, nonce_to;
@@ -93,7 +96,7 @@ cscoin_solve_challenge (gint           challenge_id,
 
             for (i = 0; i < nb_elements; i++)
             {
-                numbers[i] = cscoin_mt64_next_uint64 (&mt64);
+                cscoin_heap64_push (&numbers_heap, cscoin_mt64_next_uint64 (&mt64));
             }
 
             switch (challenge_type)
@@ -108,10 +111,11 @@ cscoin_solve_challenge (gint           challenge_id,
 
             SHA256_Init (&checksum);
 
+            guint64 number;
             gchar number_str[32];
-            for (i = 0; i < nb_elements; i++)
+            while ((number = cscoin_heap64_pop (&numbers_heap)) != CSCOIN_HEAP64_NULL)
             {
-                g_snprintf (number_str, 32, "%lu", numbers[i]);
+                g_snprintf (number_str, 32, "%lu", number);
                 SHA256_Update (&checksum, number_str, strlen (number_str));
             }
 
diff --git a/meson.build b/meson.build
index 1d1af1b..ba5cbc7 100644
--- a/meson.build
+++ b/meson.build
@@ -12,7 +12,7 @@ soup = dependency('libsoup-2.4')
 json_glib = dependency('json-glib-1.0')
 openssl = dependency('openssl')
 
-solver_lib = library('cscoin-solver', 'cscoin-solver.c', 'cscoin-mt64.c',
+solver_lib = library('cscoin-solver', 'cscoin-solver.c', 'cscoin-mt64.c', 'cscoin-heap64.c',
                      dependencies: [glib, gio, gomp, openssl])
 
 executable('cscoin-miner', 'cscoin-miner.vala',
diff --git a/tests/heap64-test.vala b/tests/heap64-test.vala
new file mode 100644
index 0000000..e69de29