Add nem_ull with shuffle

1 files changed, 30 insertions, 0 deletions

diff --git a/src/common.c b/src/common.c
index 7a8b316..5fc944e 100644
--- a/src/common.c
+++ b/src/common.c
@@ -111,3 +111,33 @@ int len_front(struct front_item * f){
   for(N=0;f!=NULL;f=f->next,N++);
   return N;
 }
+
+/* Shuffle data items starting on a certain index, in place */
+void shuffle_items(struct data * d, int start) {
+  int i, ind;
+  struct item * new_items;
+
+  if (start < 0) return;
+  if (start >= d->N) return;
+
+  new_items = (struct item *)malloc(d->N * sizeof(struct item));
+
+  /* These stay the same */
+  for(i = 0; i < start; i++) {
+    new_items[i].p = d->items[i].p;
+    new_items[i].w = d->items[i].w;
+  }
+
+  /* Shuffle the rest */
+  for(i = start; i < d->N; i++) {
+    ind = rand() % (d->N - i);
+    new_items[i].p = d->items[i+ind].p;
+    new_items[i].w = d->items[i+ind].w;
+    d->items[i+ind].p = d->items[i].p;
+    d->items[i+ind].w = d->items[i].w;
+  }
+
+  /* Replace old array */
+  free(d->items);
+  d->items = new_items;
+}