Hello everyone! Here is the description of my problem: The Program's Description: I am implementing a program in C++ that tests Prim's algorithm for finding minimum spanning trees. The objective of the program is calculating the number of seconds it takes to find the minimum spanning tree for a selected number of random graphs. What i have done up to now? I finished the implementation of the functions and the header files for the whole program. Since the source code is small, i decided for clarity reasons to attach it with this mail in order to provide a better visualization of the problem. The Problem: For some reason, i have facing some sort of "out of range" vector problem during the run time of the application. The problem is rising specifically in the lines of: 123 & 126 of the ("Prim_and_Kruskal_Algorithms.cpp") file. The Nature of the Current Source Code: The source code is without compiling errors or warning. It is properly documented with clear indentation. It is rather a short code. Requesting help: I would be really grateful if anyone can help me spotting the problem. I have attached the source code with this question. Thanks in advance for your help,