From Alan R. Feuer: "The C Puzzle Book"

Each file is a C puzzle.   If you can understand the puzzles you can understand C.

The Book is Great.   Published by Prentice Hall Software Series.    It may be out of print, but it is worth looking for.

defs.h

Appendices_1.c      

BasicType_1.c         BasicType_2.c      BasicType_3.c  

ControlFlow_1.c    ControlFlow_2.c    ControlFlow_3.c    ControlFlow_4.c

Operators_1.c    Operators_2.c    Operators_3.c    Operators_4.c    Operators_5.c    Operators_6.c

PointersAndArrays_1.c    PointersAndArrays_2.c    PointersAndArrays_3.c    PointersAndArrays_4.c 

Preprocessor_1.c    Preprocessor_2.c  

ProgrammingStyle_1.c  

StorageClasses_1.c    StorageClasses_2.c    StorageClasses_3.c    StorageClasses_4.c    StorageClasses_4a.c    StorageClasses_4b.c   

Structures_1.c      Structures_2.c    Structures_2.cpp    Structures_3.c