1. Lists C++ Standard template library list
Add the following to the top of cpp file
#include <list>
using namespace std;
E.g., list of ints
making a list of ints
list<int> myList;
Add an element to myList
myList.push_back(1);
myList.push_back(2);
Iterate through the list and print each element
for( list<int>::iterator it=myList.begin(); it!=myList.end(); ++it)
printf(“entry=%d\n”,*it);

2. Iterate through std::lists
for( list<int>::iterator it=myList.begin(); it!=myList.end(); ++it)
printf(“entry=%d\n”,*it);
for( int x : mylist)
printf(“entry=%d\n”,x);
for( int &x : mylist)
x = x + 1;
// int &x allows changes to x to be save in the list
printf(“entry=%d\n”,x); // this will show the changes made above.
for (auto &x : myList)
// I forgot that myList is a list of integers. Or, I might change myLists later and don’t want to have to change all my other code

3. Removing elements from Lists
Remove an element from the list
int elementToRemove = 2;
for( list<int>::iterator it=myList.begin(); it!=myList.end(); ++it) {
if (*it == elementToRemove)
myList.erase(it);
break; // not breaking would result in a crash }
Alternatively
myList.remove(1); // removes all elements == 1. But this requires == operator, which exists for int, but might not for other types. But == does exist for all classes used in this project

4. Example, Iterating through a list
Recall, when a hello arrives, we need to check if thisHost is in the list of neighbors included in the hello message

5. A B A A I am A I have heard: no one Have heard list Have heard list
Received message from A
if thisHost is in the helloMessage’s list of neighbors
isBidirectional = True
else
isBidirectional = False
Add A to list of unidirectional neighbors
Q: Why did we add A to the list of unidirectional neighbors and not the list of bidirectional neighbors?
A: Because A has not heard any messages from B
A: The hello message from A did not include B
I am A
I have heard: no one A B
Have heard list
Have heard list A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors A

6. Example, Iterating through a list
Recall, when a hello arrives, we need to check if thisHost is in the list of neighbors included in the hello message
Packet pkt;
If (udpSocket.checkForNewPacket(pkt, 2)>0) {
HelloMessage helloMessage;
helloMessage.getFromPacket(pkt);
//TODO: extract sender from helloMessage
// TODO: check if sender is in list of bi/unidirectional neighbors
// check if this host is in neighbor’s list of recently heard neighbors
boolean isBidirectional = False;
for(HostId &hostId : helloMessage.neighbors) {
if (thisHost == hostId) {
// yes it is
isBidirectional = True; }
Classes Packet, HelloMessage, UdpSocket, and HelloMessage are all provided
Suppose that:
helloMessage.neighors = {A,B,C}
thisHost = C
iteration1: hostId = A
If (thisHost == hostId)  if (C == A)  False
Iteration 2: hostId = B
If (thisHost == hostId)  if (C == B)  False
Iteration 3: hostId = C
If (thisHost == hostId)  if (C==C)  True
isBidirectional = True

7. Example, Iterating through a list
Recall, when a hello arrives, the time that a hello was last received from the neighbor should be updated
Packet pkt;
If (udpSocket.checkForNewPacket(pkt, 2)>0) {
HelloMessage helloMessage;
helloMessage.getFromPacket(pkt);
//TODO: ….
for (NeighborInfo &neigbor : bidirectionalNeighbors) {
if (neighbor == helloMessage.source) {
neighbor. updateTimeToCurrentTime(); }
Suppose that:
bidirectionalNeighors = {A,B,C}
helloMessage.source = C
iteration1: neighbor = A
If (neighbor == helloMessage.source)  if (A == C)  False
Iteration 2: neighbor = B
If (neighbor == helloMessage.source)  if (B == C)  False
Iteration 3: neighbor = C
If (neighbor == helloMessage.source)  if (C == C)  True
C. updateTimeToCurrentTime();

8. Example, Iterating through a list
for (NeighborInfo &neigbor : bidirectionalNeighbors) {
if (neighbor == helloMessage.source) {
neighbor. updateTimeToCurrentTime(); }
Suppose that:
bidirectionalNeighors = {A,B,C}
helloMessage.source = C
iteration1: neighbor = A
If (neighbor == helloMessage.source)  if (A == C)  False
Iteration 2: neighbor = B
If (neighbor == helloMessage.source)  if (B == C)  False
Iteration 3: neighbor = C
If (neighbor == helloMessage.source)  if (C == C)  True
C. updateTimeToCurrentTime();
C. timeWhenLastHelloArrived = current time
Wait, did we just change timeWhenLastHelloArrived in some object, or did we change it in the list?

9. Example, Iterating through a list
for (NeighborInfo &neigbor : bidirectionalNeighbors) {
if (neighbor == helloMessage.source) {
neighbor. updateTimeToCurrentTime(); }
Suppose that:
bidirectionalNeighors = {{hostId=A, timeWhenLastHelloArrived=12:00}, {hostId=B, timeWhenLastHelloArrived=12:01}, {hostId=C; timeWhenLastHelloArrived=12:00}}
helloMessage.source = C
iteration1: neighbor = {hostId=A, timeWhenLastHelloArrived=12:00}
If (neighbor == helloMessage.source)  if (A == C)  False
Iteration 2: neighbor = {hostId=B, timeWhenLastHelloArrived=12:01}
If (neighbor == helloMessage.source)  if (B == C)  False
Iteration 3: neighbor = {hostId=C, timeWhenLastHelloArrived=12:00}
If (neighbor == helloMessage.source)  if (C == C)  True
C. updateTimeToCurrentTime();
C. timeWhenLastHelloArrived = current time
Wait, did we just change timeWhenLastHelloArrived in some object, or did we change it in the list?
for (NeighborInfo &neigbor : bidirectionalNeighbors)
for (NeighborInfo neigbor : bidirectionalNeighbors)
Yes, we are working with the ACTUAL objects in the list
No, we are working with COPIES objects in the list

10. Example, Iterating through a list
for (NeighborInfo &neigbor : bidirectionalNeighbors) {
if (neighbor == helloMessage.source) {
neighbor. updateTimeToCurrentTime(); }

11. Example, Iterating through a list
Recall, sometimes we might need to remove an element from a list
// check if neighbor has timed out
time(&currentTime); // get current time
for(NeighborInfo &neighbor : unidirectionalNeighbors) {
if (difftime(currentTime, neighbor.timeWhenLastHelloArrived) > 40) {
// remove old neighbor
unidirectionalNeighbors .remove(neighbor);
break; }
Without the break, your code will crash
list item
list item
list item
list item