Create Dijkstra's_Algorithm.cpp

CPP/Dijkstra's_Algorithm.cpp

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+#include <iostream>
+#include <vector>
+#include <queue>
+#include <climits> // for INT_MAX
+
+using namespace std;
+
+// A pair to represent the node and its associated weight
+typedef pair<int, int> pii;
+
+// Dijkstra's algorithm function to find the shortest path
+void dijkstra(int source, vector<vector<pii>> &adj, int n) {
+ // Create a priority queue (min-heap)
+ priority_queue<pii, vector<pii>, greater<pii>> pq;
+
+ // Vector to store the shortest distance from the source to each node
+ vector<int> dist(n, INT_MAX);
+
+ // Distance to the source is 0
+ dist[source] = 0;
+
+ // Push the source into the priority queue
+ pq.push({0, source});
+
+ while (!pq.empty()) {
+ int curr_dist = pq.top().first; // Current distance from source
+ int u = pq.top().second; // Current node
+ pq.pop();
+
+ // If the popped node's distance is not the shortest, skip processing
+ if (curr_dist > dist[u]) {
+ continue;
+ }
+
+ // Iterate over all the adjacent nodes of u
+ for (auto &neighbor : adj[u]) {
+ int v = neighbor.first; // Neighboring node
+ int weight = neighbor.second; // Edge weight
+
+ // Relax the edge (u, v) if a shorter path is found
+ if (dist[u] + weight < dist[v]) {
+ dist[v] = dist[u] + weight;
+ pq.push({dist[v], v});
+ }
+ }
+ }
+
+ // Print the shortest distance to all nodes from the source
+ cout << "Shortest distances from source node " << source << ":\n";
+ for (int i = 0; i < n; ++i) {
+ if (dist[i] == INT_MAX) {
+ cout << "Node " << i << ": Unreachable\n";
+ } else {
+ cout << "Node " << i << ": " << dist[i] << "\n";
+ }
+ }
+}
+
+int main() {
+ int n, m; // Number of nodes and edges
+ cout << "Enter the number of nodes and edges: ";
+ cin >> n >> m;
+
+ // Adjacency list to store the graph (node, weight)
+ vector<vector<pii>> adj(n);
+
+ cout << "Enter the edges in the format (u v weight):\n";
+ for (int i = 0; i < m; ++i) {
+ int u, v, weight;
+ cin >> u >> v >> weight;
+
+ // For an undirected graph, you need to add both directions
+ adj[u].push_back({v, weight});
+ adj[v].push_back({u, weight});
+ }
+
+ int source;
+ cout << "Enter the source node: ";
+ cin >> source;
+
+ // Run Dijkstra's algorithm from the source node
+ dijkstra(source, adj, n);
+
+ return 0;
+}