拓扑排序，如果有圈则提示，无圈则输出拓扑排序的结果-Topological sort, if there circle the prompt, the output acyclic topological sort results

Topological sort for digital circuit.Describe a circuit in a input.txt file and run the program to get the topological sort.-Topological sort for digital circuit.Describe a circuit in a input.txt file and run the program to get the topological sort