# Create the Shortest Path Finder with Dijkstra's Algorithm in C

June 19, 2024
Dr. Timothy
🇨🇭 Switzerland
C
Dr. Timothy Shah obtained his PhD in Computer Science from ETH Zurich in Zurich, Switzerland. With 6 years of experience under his belt, he has successfully completed over 600 C programming assignments. Dr. Shah's research focuses on artificial intelligence and machine learning, and his deep understanding of these concepts enables him to deliver exceptional solutions to programming problems.
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Key Topics
• Exploring Dijkstra's Algorithm for Shortest Path in C
• Block 1: Main Function
• Block 3: Freeing the Graph
• Block 4: Dijkstra's Algorithm
• Block 5: Constants and Structures
• Conclusion

In this guide, we will guide you through the process of finding the shortest path on a graph using Dijkstra's algorithm in the C programming language. This is a fundamental concept in graph theory and is often used to solve real-world problems, such as finding the shortest route between locations on a map or optimizing network routing. Understanding how Dijkstra's algorithm works and implementing it in C will equip you with a powerful tool for tackling complex optimization challenges, making it a valuable skill for students, programmers, and anyone interested in algorithmic problem-solving.

## Exploring Dijkstra's Algorithm for Shortest Path in C

Explore Dijkstra's Algorithm for Shortest Path in C on our website, where we provide comprehensive guidance and practical examples. If you need help with your C assignment, this resource will equip you with valuable insights to tackle complex optimization challenges. Whether you're a student aiming to enhance your programming skills or a professional seeking solutions for real-world graph problems, our content offers the knowledge and support you need to succeed. Discover the power of Dijkstra's Algorithm and its applications in C programming.

## Block 1: Main Function

``````c #include #include #include "structname.h" int main() { // Prompt for the file to be processed and load it as a graph object printf("Enter File Name:\n"); char filename[MAX_STR_LEN]; fgets(filename, MAX_STR_LEN, stdin); filename[strlen(filename) - 1] = '\0'; Graph* graph = loadGraph(filename); // Prompt for the starting node and calculate shortest paths printf("Start Node:\n"); char line[MAX_STR_LEN]; int startingNode; fgets(line, MAX_STR_LEN, stdin); sscanf(line, "%d", &startingNode); printf("Running Dijkstra on graph.\n"); printf("Input File: %s\n", filename); printf("Start Node: %d\n", startingNode); findShortestPath(graph, startingNode); // Clean up and exit freeGraph(graph); return 0; } ``` ```

• This block is the main function that orchestrates the program.
• It first asks for the filename containing graph data and the starting node.
• Then, it calls the `loadGraph` function to load the graph data.
• After loading the graph, it calls the `findShortestPath` function to calculate the shortest paths.
• Finally, it releases memory and exits.

``````c Graph* loadGraph(const char* filename) { // Attempt to open the file, terminate the program if the file does not exist or cannot be read. FILE* file = fopen(filename, "r"); if (!file) { printf("Error: Failed to open the file.\n"); exit(1); } // Load the number of vertices and the connections between them Graph* graph = (Graph*)malloc(sizeof(Graph)); fscanf(file, "%d", &graph->size); graph->distances = (int**)malloc(sizeof(int*) * graph->size); for (int i = 0; i < graph->size; i++) graph->distances[i] = (int*)malloc(sizeof(int) * graph->size); // Vertices have no connection to each other by default, hence the distance is set to 0. int fromVertex, toVertex; for (fromVertex = 0; fromVertex < graph->size; fromVertex++) for (toVertex = 0; toVertex < graph->size; toVertex++) graph->distances[fromVertex][toVertex] = 0; // Now connect the vertices int distance; while (fscanf(file, "%d %d %d", &fromVertex, &toVertex, &distance) == 3) graph->distances[fromVertex][toVertex] = distance; return graph; } ``` ```

• This block defines the `loadGraph` function that reads the graph data from a file.
• It opens the file, reads the number of vertices, and creates a graph structure.
• It then connects vertices based on the input file and returns the graph.

## Block 3: Freeing the Graph

``````c void freeGraph(Graph* graph) { for (int i = 0; i < graph->size; i++) free(graph->distances[i]); free(graph->distances); free(graph); } ``` ```

• This block defines the `freeGraph` function, which frees memory allocated for the graph structure.

## Block 4: Dijkstra's Algorithm

```<code ignore--minify class="code-view">```c void freeGraph(Graph* graph) { for (int i = 0; i &lt; graph-&gt;size; i++) free(graph-&gt;distances[i]); free(graph-&gt;distances); free(graph); } ``` </code> ```

• This block defines the `findShortestPath` function, which implements Dijkstra's algorithm.
• It initializes data structures, such as an array of nodes, for the algorithm.
• It then performs Dijkstra's algorithm to find the shortest paths from the starting node to all other nodes.
• Finally, it prints the results, showing the shortest distances from the starting node to each node.

## Block 5: Constants and Structures

``````c #define MAX_STR_LEN 100 #define TRUE 1 #define FALSE 0 typedef struct Graph Graph; struct Graph { int** distances; /**< A 2 dimensional array that keeps track the connection of vertices. The indices of the array are the vertices, the content are the distances. */ int size; /**< The number of vertices in the graph */ }; typedef struct Node Node; struct Node { int distance; /**< Estimated sorted distance from this node to a chosen shortest path to another node */ int isVisited; /**< Indicates if the node has been processed or not when doing Dijkstra's algorithm */ }; ``` ```

• This block defines constants and structures used in the program.
• It includes the definition of the `Graph` structure, which holds the graph data.
• It defines the `Node` structure, which is used in Dijkstra's algorithm.
• It also sets some constants for readability.

## Conclusion

By following this guide, you'll gain a strong foundation in implementing Dijkstra's algorithm in C, which can be applied to various graph-related problems. Whether you're a student looking for programming homework help or a programmer seeking to enhance your knowledge, this guide will provide valuable insights and practical examples. With this newfound knowledge, you'll be better equipped to tackle real-world challenges, from optimizing transportation routes to network pathfinding. The ability to find the shortest path efficiently is a highly sought-after skill in the fields of computer science, data analysis, and beyond, making this guides a valuable resource for your journey into the world of algorithms and problem-solving.

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