Shortest path given beginning and end of a weighted graph - c++

Question

I have to read in a file to create a weighted graph. The shortest path must be found using input from the file. File will be structured as first line = numVertices and every line below that has 3 numbers given as : 0 1 2 where 0 is start of an edge, 1 is the end of the edge, and 2 is the weight. I've tried implementing an adjacency matrix when creating my graph but have had no luck. Any suggestions would be greatly appreciated.
Have tried restructuring the way I read in my file and have also tried adjusting my findShortestPath function.
void createGraph(string file_name) //Function to create a graph based on a file, whose name is file_name.
{
ifstream f(file_name);
if (f.fail())
{
return;
}
string line;
getline(f, line);
int num = stoi(line);
numVertices = num;
int data[50][50];
string line2;
int num1 = 0, num2 = 0, num3 = 0;
while (!f.eof())
{
f >> num1;
f >> num2;
f >> line2;
num3 = stoi(line2);
data[num1][num2] = num3;
}
}
//////////////////shortest path function
string findShortestPath(int start, int end)
{
int data[numVertices][numVertices];
int dist[numVertices];
bool sptSet[numVertices];
int parent[numVertices];
for (int i = 0; i < numVertices; i++)
{
parent[0] = -1;
dist[i] = INT_MAX;
sptSet[i] = false;
}
dist[start] = 0;
for (int count = 0; count < numVertices - 1; count++)
{
int u = minDistance(dist, sptSet);
sptSet[u] = true;
if (sptSet[u] == end)
break;
for (int v = 0; v < numVertices; v++)
if (!sptSet[v] && data[u][v] && dist[u] + data[u][v] < dist[v])
{
parent[numVertices] = end;
dist[v] = dist[u] + data[u][v];
}
}
printSolution(parent);
Output is not outputting shortest path and is printing random numbers.

Answer 1

In your findShortestPath function data[numVertices][numVertices] is not the same as the data variable in your createGraph function.
Look at this https://www.geeksforgeeks.org/scope-of-variables-in-c/ or try finding other sources on scope of variables.

Answer 2

In your function findShortestPath you have declared a local array called data, which is supposed to store the adjacency matrix data. However, you have never written any data into it! Consider passing the matrix as a function argument. Your function signature should look something like this:
findShortestPath(int** data, int numVertices, int start, int end)
Also, avoid using VLA as it is not part of the standard. Consider creating a two dimensional array on the heap using new. (and don't forget to do delete[] after you are done!)
Or you can use std::vector<std::vector<int>>, if you don't want to manage your array's lifetime manually.