diff --git a/semester3/exercises/exercise2.13.c b/semester3/exercises/exercise2.13.c
index 61a3a39..103d322 100644
--- a/semester3/exercises/exercise2.13.c
+++ b/semester3/exercises/exercise2.13.c
@@ -1,16 +1,12 @@
 #include <math.h>
 #include <stdio.h>
 #include <time.h>
-
 void printTime(clock_t end, clock_t start) {
   printf("Took %lf to calculate.\n", ((double)(end - start)) / CLOCKS_PER_SEC);
 }
-
 void calculate(long long N) {
   clock_t end, start;
-
   start = clock();
-
   for (int i = 1, root = (int)floor(sqrt((double)N)); i < root; i++) {
     if (N % i == 0) {
       end = clock();
@@ -19,19 +15,16 @@ void calculate(long long N) {
       return;
     }
   }
-
   end = clock();
   printTime(end, start);
   printf("%lld is prime\n", N);
   return;
 }
-
 int main(void) {
   long long test[] = {1048575, 1099511627775};
   for (int i = 0; i < 2; i++) {
     calculate(test[i]);
     printf("\n");
   }
-
   return 0;
 }
diff --git a/semester3/exercises/exercise2.6.c b/semester3/exercises/exercise2.6.c
index b62bcbc..d6719c3 100644
--- a/semester3/exercises/exercise2.6.c
+++ b/semester3/exercises/exercise2.6.c
@@ -5,7 +5,7 @@ int counter = 0;
 
 void getTime(int N, clock_t start_t, time_t end_t) {
   double runningTime;
-  runningTime = ((double) (end_t - start_t)) / CLOCKS_PER_SEC;
+  runningTime = ((double)(end_t - start_t)) / CLOCKS_PER_SEC;
 
   printf("%d: Took %lf sec\n", counter++, runningTime);
 }
diff --git a/semester3/exercises/exercise3.10.c b/semester3/exercises/exercise3.10.c
new file mode 100644
index 0000000..20eb09b
--- /dev/null
+++ b/semester3/exercises/exercise3.10.c
@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct ListNode {
+  int val;
+  struct ListNode *next;
+} ListNode;
+
+ListNode *appendNode(ListNode *node, int val) {
+  ListNode *new = malloc(sizeof(ListNode));
+  node->next = new;
+
+  new->next = NULL;
+  new->val = val;
+
+  return new;
+}
+
+void freeNode(ListNode *head) {
+  if (head != NULL) {
+    ListNode * ptr = head->next;
+    free(head);
+    freeNode(ptr);
+  }
+}
+
+void deleteNode(ListNode *node) {
+  // deletes node after this one.
+  ListNode* tmp = node->next;
+  node->next = node->next->next;
+
+  // printf("Deleted: %d\n", tmp->val);
+
+  tmp->next = NULL;
+  free(tmp);
+}
+
+void printNode(ListNode *head) {
+  ListNode *ptr = head;
+
+  while (ptr != NULL) {
+    printf("%d->", ptr->val);
+    ptr = ptr->next;
+  }
+
+  printf("NULL\n");
+}
+
+int main(void) {
+  // N people, M passes
+  int N, M;
+  scanf("%d%d", &M, &N);
+
+  // construct ring
+  ListNode *head = malloc(sizeof(ListNode));
+  ListNode *ptr = head;
+
+  for (int i = 1; i <= N; i++) {
+    ptr = appendNode(ptr, i);
+  }
+
+  printNode(head->next);
+  // enclose the ring
+  ptr->next = head->next;
+
+  // start simulation
+  ListNode** cur = &head;
+  ListNode** tmp;
+  int pass = 0;
+
+  while ((*cur) && (*cur)->next && (*cur)->next->next) {
+    // printf("Potato: %d\n", (*cur)->next->val);
+    if (pass == M) {
+      // kick this player, and continue.
+      tmp = cur;
+      deleteNode(*cur);
+      pass = 0;
+    } else {
+      cur = &(*cur)->next;
+      pass++;
+    }
+  }
+  printf("Remaining: %d\n", (*cur)->next->val);
+
+  free(head);
+  free(cur);
+  return 0;
+}
diff --git a/semester3/exercises/exercise3.6.c b/semester3/exercises/exercise3.6.c
new file mode 100644
index 0000000..ec2be72
--- /dev/null
+++ b/semester3/exercises/exercise3.6.c
@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct ListNode {
+  int val;
+  struct ListNode *next;
+} ListNode;
+
+ListNode *appendNode(ListNode *node, int val) {
+  ListNode *new = malloc(sizeof(ListNode));
+  node->next = new;
+
+  new->next = NULL;
+  new->val = val;
+
+  return new;
+}
+
+void freeNode(ListNode *head) {
+  ListNode *ptr = head;
+  do {
+    head = ptr;
+    ptr = ptr->next;
+    free(head);
+  } while (ptr != NULL);
+}
+
+void printNode(ListNode *head) {
+  ListNode *ptr = head;
+
+  while (ptr != NULL) {
+    printf("%d->", ptr->val);
+    ptr = ptr->next;
+  }
+
+  printf("NULL\n");
+}
+
+ListNode *addList(ListNode *l, ListNode *r) {
+  ListNode *head = malloc(sizeof(ListNode));
+  head->val = l->val + r->val;
+
+  ListNode *ptr = head;
+  ListNode *ptrL = l->next;
+  ListNode *ptrR = r->next;
+  while (ptrL && ptrR) {
+    ptr = appendNode(ptr, ptrL->val + ptrR->val);
+    ptrL = ptrL->next;
+    ptrR = ptrR->next;
+  }
+
+  while (ptrL) {
+    ptr = appendNode(ptr, ptrL->val);
+    ptrL = ptrL->next;
+  }
+
+  while (ptrR) {
+    ptr = appendNode(ptr, ptrR->val);
+    ptrR = ptrR->next;
+  }
+
+  return head;
+}
+
+int main(void) {
+  ListNode *l = malloc(sizeof(ListNode));
+  ListNode *r = malloc(sizeof(ListNode));
+
+  ListNode *ptrL = l;
+  ListNode *ptrR = r;
+
+  // input
+  int lLen, rLen;
+  scanf("%d", &lLen);
+  scanf("%d", &rLen);
+  int temp;
+
+  for (int i = 0; i < lLen; i++) {
+    scanf("%d", &temp);
+    ptrL = appendNode(ptrL, temp);
+  }
+  printNode(l->next);
+
+  for (int i = 0; i < rLen; i++) {
+    scanf("%d", &temp);
+    ptrR = appendNode(ptrR, temp);
+  }
+  printNode(r->next);
+
+  // add
+  ListNode *ans = addList(l->next, r->next);
+  printNode(ans);
+
+  freeNode(l);
+  freeNode(r);
+  freeNode(ans);
+
+  return 0;
+}