# Find indegree and outdegree of a directed graph in kotlin

Kotlin program for Find indegree and outdegree of a directed graph. Here problem description and explanation.

``````/*
Kotlin Program for
Show degree of vertex in directed graph
*/
class AjlistNode
{
// Vertices node key
var id: Int;
var next: AjlistNode ? ;
constructor(id: Int)
{
// Set value of node key
this.id = id;
this.next = null;
}
}
class Vertices
{
var data: Int;
var next: AjlistNode ? ;
var last: AjlistNode ? ;
constructor(data: Int)
{
this.data = data;
this.next = null;
this.last = null;
}
}
class Graph
{
// Number of Vertices
var size: Int;
var node: Array < Vertices ? > ;
constructor(size: Int)
{
// Set value
this.size = size;
this.node = Array(size)
{
null
};
this.setData();
}
// Set initial node value
fun setData(): Unit
{
if (this.size <= 0)
{
println("\nEmpty Graph");
}
else
{
var index: Int = 0;
while (index < this.size)
{
// Set initial node value
this.node[index] = Vertices(index);
index += 1;
}
}
}
//  Handling the request of adding new edge
fun addEdge(start: Int, last: Int): Unit
{
if (start >= 0 && start < this.size &&
last >= 0 && last < this.size)
{
// Safe connection
val edge: AjlistNode = AjlistNode(last);
if (this.node[start]?.next == null)
{
this.node[start]?.next = edge;
}
else
{
// Add edge at the end
this.node[start]?.last?.next = edge;
}
// Get last edge
this.node[start]?.last = edge;
}
else
{
// When invalid nodes
println("\nHere Something Wrong");
}
}
fun printGraph(): Unit
{
if (this.size > 0)
{
var index: Int = 0;
// Print graph ajlist Node value
while (index < this.size)
{
print("\nAdjacency list of vertex " + index + " : ");
var temp: AjlistNode ? = this.node[index]?.next;
while (temp != null)
{
// Display graph node
print(" " + this.node[temp.id]?.data);
// Visit to next edge
temp = temp.next;
}
index += 1;
}
}
}
// Find indegree and outdegree of
// each nodes of a given graph
fun findDegree(indegree: Array < Int > ,
outdegree: Array < Int > ): Unit
{
var temp: AjlistNode ? ;
var length: Int = 0;
var i: Int = 0;
while (i < this.size)
{
temp = this.node[i]?.next;

while (temp != null)
{
// Update indegree
indegree[temp.id] += 1;
temp = temp.next;
length += 1;
}
// Set outdegree value
outdegree[i] = length;
i += 1;
length = 0;
}
}
fun showDegree(): Unit
{
if (this.size > 0)
{
val indegree: Array < Int > = Array(this.size)
{
0
};
val outdegree: Array < Int > = Array(this.size)
{
0
};

// Find degree
this.findDegree(indegree, outdegree);
println("\n");
var i: Int = 0;
// Display result
while (i < this.size)
{
println("Node [" + i + "] indegree [" +
indegree[i] + "] outdegree [" +
outdegree[i] + "]");
i += 1;
}
}
else
{
print("Empty Graph");
}
}
}
fun main(args: Array < String > ): Unit
{
// 6 implies the number of nodes in graph
val g: Graph = Graph(6);
// Connected two node with Edges
g.printGraph();
// Test
g.showDegree();
}``````

Output

``````Adjacency list of vertex 0 :  1 2 5
Adjacency list of vertex 1 :
Adjacency list of vertex 2 :  3
Adjacency list of vertex 3 :  1
Adjacency list of vertex 4 :  0 1
Adjacency list of vertex 5 :  0 2

Node [0] indegree [2] outdegree [3]
Node [1] indegree [3] outdegree [0]
Node [2] indegree [2] outdegree [1]
Node [3] indegree [1] outdegree [1]
Node [4] indegree [0] outdegree [2]
Node [5] indegree [1] outdegree [2]``````

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