Merge pull request #645 from Enmilo-dev/main

Graph builder and printer

Author: Karanjot786

CPP/data_structures/trees/graph.cpp

@@ -0,0 +1,55 @@
+/*
+ * Graph Adjacency List Implementation
+ *
+ * Description:
+ * This program implements an undirected graph using an adjacency list representation.
+ * Each vertex maintains a list of its adjacent vertices. The graph supports adding edges
+ * between vertices and printing the complete adjacency list structure.
+ *
+ * Time Complexity:
+ * - addEdge(): O(1) - Constant time insertion at the end of the list
+ * - print(): O(V + E) - where V is the number of vertices and E is the number of edges
+ *
+ * Space Complexity:
+ * - O(V + E) - Stores V adjacency lists with a total of 2E entries (each edge stored twice)
+ *
+ * Author: @Enimi-dev
+ */
+
+#include <iostream>
+#include <list>
+#include <vector>
+class Graph{
+    int v;  // Number of vertices in the graph
+    std::list<int> *arr;  // Array of lists to represent adjacency list
+public:
+    Graph(int val) {  // Constructor to initialize the graph with 'val' vertices
+        this->v = val;
+        arr = new std::list<int>[v];
+    }
+    void addEdge(int u, int v) {  // Add an undirected edge between vertex u and vertex v
+        arr[v].push_back(u);
+        arr[u].push_back(v);
+    }
+    void print() {  // Print the adjacency list representation of the graph
+        for (int i=0; i<v; i++) {
+            std::cout << i << " : ";
+            for (auto val: arr[i]) {
+                std::cout<<val<<" ";
+            }
+            std::cout<<std::endl;
+        }
+    }
+};
+int main() {
+    Graph g(5);  // Create a graph with 5 vertices (0 to 4)
+    g.addEdge(0, 1);
+    g.addEdge(1, 2);
+    g.addEdge(1, 3);
+    g.addEdge(2, 3);
+    g.addEdge(2, 4);
+
+    g.print();
+
+    return 0;
+}