# Node and Edge Functions

YouTube Video`add node`

: will add a node to the graph with the given value if our graph still has room. Procedurally, we will try to put the node in the first empty place we find. To do this, we start with`IDX`

equal to negative one then loop through all of the indexes of the graphs`nodes`

attribute. At each index, we check if that entry is equal to the value we are trying to add. This will check if the value is already in our graph. If there is nothing in that entry and the`IDX`

variable is still negative one, then we will set`IDX`

equal to that index. We continue looping through the`nodes`

attribute until we reach the end. It is possible that there is more than one open space in the`nodes`

attribute. Thus, by checking if`IDX`

is still negative one we can make sure to put`value`

in the first empty spot. Once we finish going through`nodes`

we check to see if we ever found an open spot. If`IDX`

is still negative one, this would indicate that there was no room. Otherwise, we put`value`

into`nodes`

at spot`IDX`

and increment the size.

```
function ADDNODE(VALUE)
IDX = -1
for NODE in NODES
if NODE is VALUE
return NODE's index
if NODE has no entry and IDX is -1
IDX = NODE's index
if IDX is not -1
add VALUE to NODES at position IDX
increment SIZE
return IDX
```

`remove node`

: will remove a node to the graph with the given value if our graph has the node. We will set the node to be empty and remove any edges that may be attached to it.

```
function REMOVENODE(IDX)
if IDX is in the range of our indexes
if NODES at position IDX is not empty
set NODES at IDX to be empty
decrement SIZE by one
for J in node indexes
set EDGES (J,IDX) equal to infinity
set EDGES (IDX,J) equal to infinity
return true
else
return false
else
return false
```

`add edge`

: will add an edge with the given weight which goes from the source node to the target node

```
function ADDEDGE(SOURCE, TARGET, WEIGHT)
if SOURCE and TARGET are both in the range of our node indexes
set EDGES(SOURCE, TARGET) equal to WEIGHT
return true
else
return false
```

`remove edge`

: will remove the edge which goes from the source node to the target node

```
function REMOVEEDGE(SOURCE, TARGET)
if SOURCE and TARGET are both in the range of our node indexes
if EDGES(SOURCE, TARGET) is not equal to infinity
set EDGES(SOURCE, TARGET) equal to infinity
return true
else
return false
else
return false
```

`add undirected edge`

: will add two edges with the given weight between the two given nodes

```
function ADDUNDIRECTEDEDGE(NODE1, NODE2, WEIGHT)
RES = ADDEDGE(NODE1, NODE2, WEIGHT)
RES = RES and ADDEDGE(NODE2, NODE1, WEIGHT)
return RES
```

`remove undirected edge`

: will remove two edges between the two given nodes. We can utilize the remove edge function on ‘NODE1’ to ‘NODE2’ and then on ‘NODE2’ to ‘NODE1’.

```
function REMOVEUNDIRECTEDEDGE(NODE1, NODE2)
RES = REMOVEEDGE(NODE1, NODE2)
RES = RES and REMOVEEDGE(NODE2, NODE1)
return RES
```