From 5d9e3d30546c800704b6e15b79da56888cfc4e7f Mon Sep 17 00:00:00 2001
From: AkashMarkad <79374621+AkashMarkad@users.noreply.github.com>
Date: Sat, 30 Oct 2021 08:39:18 +0530
Subject: [PATCH] Create Graph_Adjacency_list.cpp

---
 Graph_Adjacency_list.cpp | 100 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 Graph_Adjacency_list.cpp

diff --git a/Graph_Adjacency_list.cpp b/Graph_Adjacency_list.cpp
new file mode 100644
index 0000000..cc4e8b7
--- /dev/null
+++ b/Graph_Adjacency_list.cpp
@@ -0,0 +1,100 @@
+#include <iostream>
+using namespace std;
+// stores adjacency list items
+struct adjNode {
+    int val, cost;
+    adjNode* next;
+};
+// structure to store edges
+struct graphEdge {
+    int start_ver, end_ver, weight;
+};
+class DiaGraph{
+    // insert new nodes into adjacency list from given graph
+    adjNode* getAdjListNode(int value, int weight, adjNode* head)   {
+        adjNode* newNode = new adjNode;
+        newNode->val = value;
+        newNode->cost = weight;
+         
+        newNode->next = head;   // point new node to current head
+        return newNode;
+    }
+    int N;  // number of nodes in the graph
+public:
+    adjNode **head;                //adjacency list as array of pointers
+    // Constructor
+    DiaGraph(graphEdge edges[], int n, int N)  {
+        // allocate new node
+        head = new adjNode*[N]();
+        this->N = N;
+        // initialize head pointer for all vertices
+        for (int i = 0; i < N; ++i)
+            head[i] = nullptr;
+        // construct directed graph by adding edges to it
+        for (unsigned i = 0; i < n; i++)  {
+            int start_ver = edges[i].start_ver;
+            int end_ver = edges[i].end_ver;
+            int weight = edges[i].weight;
+            // insert in the beginning
+            adjNode* newNode = getAdjListNode(end_ver, weight, head[start_ver]);
+             
+                        // point head pointer to new node
+            head[start_ver] = newNode;
+             }
+    }
+      // Destructor
+     ~DiaGraph() {
+    for (int i = 0; i < N; i++)
+        delete[] head[i];
+        delete[] head;
+     }
+};
+// print all adjacent vertices of given vertex
+void display_AdjList(adjNode* ptr, int i)
+{
+    while (ptr != nullptr) {
+        cout << "(" << i << ", " << ptr->val
+            << ", " << ptr->cost << ") ";
+        ptr = ptr->next;
+    }
+    cout << endl;
+}
+// graph implementation
+int main()
+{
+    // graph edges array.
+    graphEdge edges[] = {
+        // (x, y, w) -> edge from x to y with weight w
+        {0,1,2},{0,2,4},{1,4,3},{2,3,2},{3,1,4},{4,3,3}
+    };
+    int N = 6;      // Number of vertices in the graph
+    // calculate number of edges
+    int n = sizeof(edges)/sizeof(edges[0]);
+    // construct graph
+    DiaGraph diagraph(edges, n, N);
+    // print adjacency list representation of graph
+    cout<<"Graph adjacency list "<<endl<<"(start_vertex, end_vertex, weight):"<<endl;
+    for (int i = 0; i < N; i++)
+    {
+        // display adjacent vertices of vertex i
+        display_AdjList(diagraph.head[i], i);
+    }
+    return 0;
+}
+Output:
+
+Output:
+
+Graph adjacency list
+
+(start_vertex, end_vertex, weight):
+
+(0, 2, 4) (0, 1, 2)
+
+(1, 4, 3)
+
+(2, 3, 2)
+
+(3, 1, 4)
+
+(4, 3, 3)