#C++ data structure
#Add new data structure: singly linked list, fan xinping 2017.02.01 file: singly_linked_list.h test.cpp compile: g++ singly_linked_list.h test.cpp -o main -std=c++11 add Iterator for singly linked list, fan xinping 2017.02.17
#Add new data structure: doubly linked list, fan xinping 2017.02.02 file: doubly_linked_list.h test.cpp compile: g++ singly_linked_list.h test.cpp -o main -std=c++11
#Add new data structure: circularly linked list, fan xinping 2017.02.04 file: circularly_linked_list.h test.cpp compile: g++ circularly_linked_list.h test.cpp -o main -std=c++11