[Solved] CPMSC465 Assignment4 Part1-Find-negative-cycle

Given a directed graph G = (V,E) with edge length l(e) and a source vertex s. Find out if there is a negative cycle in G. A negative cycle in a graph is a cycle with negative length.

# Input

The graph has `n` vertices and `m` edges.There are m + 1 lines, the first line gives three numbers `n`,`m` and `s`(1 <= s <=n), describing the number of vertices, the number of edges and the source vertex. Each of the following lines contains three integers `a`, `b` and `c`, meaning there is an edge (a,b) belong to E and the length of the edge is c. All the numbers in a line are separated by space. (`1 <= a,b <= n`)

1 <= `n` <= 1000, 1 <= `m` <= 5000, and the length of `edge` is in the range of [-1000, 1000]. You can assume that all the vertices are reachable from `s`.

Your code should read the input from standard input (e.g.using functions `input()/raw_input()` in Python and `cin/scanf` in C++).

# Output

One line, if there is a negative cycle, output should be True. If not, output should be False.

Your code should write the output to standard output (e.g. using functions `print` in Python and `cout/printf` in C++).

# Requirement

Your algorithm should run in O(nm) time.

Time limtation: 5 seconds.

Memory limitation: 1.0 GB.

# Environment

Your code will be running on Ubuntu 18.04.5.

Now only accept C++ and Python2/Python3 code, g++ version 7.5.0 and Python versions are Python 2.7.17 and Python 3.6.9.

# Examples and Testing

Some examples (e.g., input-x.txt and output-x.txt, x = 1, 2) are provided.A figure corresponding input-1 can be found in this repo too.For Python code, try the following to test your code`python ./solution.py < input-x.txt > my-output-x.txt`For C++ code, try the following to test your code`g++ -o mybinary solution.cpp./mybinary < input-x.txt > my-output-x.txt`

Your output `my-output-x.txt` needs to be *match exactly* to the given `output-x.txt`.On Unix-based systems you can use `diff` to compare them:`diff my-output-x.txt output-x.txt`On Windows you can use `fc` to compare them:`fc my-output-x.txt output-x.txt`