Add a simple class stack, and example

data_structure/stk/makefile

@@ -0,0 +1,13 @@
+CC= g++
+CFLAGS = -c -Wall
+
+all: clean main test_stack
+stack.o: stack.cpp
+	$(CC) $(CFLAGS) stack.cpp
+test_stack: stack.o
+	$(CC) test_stack.cpp stack.o -o stk
+main: stack.o
+	$(CC) main.cpp stack.o -o main
+
+clean:
+	rm *o stk main