YES

We show the termination of the TRS R:

  f(a(),a()) -> f(a(),b())
  f(a(),b()) -> f(s(a()),c())
  f(s(X),c()) -> f(X,c())
  f(c(),c()) -> f(a(),a())

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(a(),a()) -> f#(a(),b())
p2: f#(a(),b()) -> f#(s(a()),c())
p3: f#(s(X),c()) -> f#(X,c())
p4: f#(c(),c()) -> f#(a(),a())

and R consists of:

r1: f(a(),a()) -> f(a(),b())
r2: f(a(),b()) -> f(s(a()),c())
r3: f(s(X),c()) -> f(X,c())
r4: f(c(),c()) -> f(a(),a())

The estimated dependency graph contains the following SCCs:

  {p1, p2, p3, p4}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(a(),a()) -> f#(a(),b())
p2: f#(a(),b()) -> f#(s(a()),c())
p3: f#(s(X),c()) -> f#(X,c())
p4: f#(c(),c()) -> f#(a(),a())

and R consists of:

r1: f(a(),a()) -> f(a(),b())
r2: f(a(),b()) -> f(s(a()),c())
r3: f(s(X),c()) -> f(X,c())
r4: f(c(),c()) -> f(a(),a())

The set of usable rules consists of

  (no rules)

Take the reduction pair:

  lexicographic combination of reduction pairs:
  
    1. lexicographic path order with precedence:
    
      precedence:
      
        c > s > f# > b > a
      
      argument filter:
    
        pi(f#) = 1
        pi(a) = []
        pi(b) = []
        pi(s) = 1
        pi(c) = []
    
    2. lexicographic path order with precedence:
    
      precedence:
      
        c > s > b > f# > a
      
      argument filter:
    
        pi(f#) = [1]
        pi(a) = []
        pi(b) = []
        pi(s) = 1
        pi(c) = []
    
    3. lexicographic path order with precedence:
    
      precedence:
      
        c > s > b > a > f#
      
      argument filter:
    
        pi(f#) = []
        pi(a) = []
        pi(b) = []
        pi(s) = [1]
        pi(c) = []
    

The next rules are strictly ordered:

  p4

We remove them from the problem.

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(a(),a()) -> f#(a(),b())
p2: f#(a(),b()) -> f#(s(a()),c())
p3: f#(s(X),c()) -> f#(X,c())

and R consists of:

r1: f(a(),a()) -> f(a(),b())
r2: f(a(),b()) -> f(s(a()),c())
r3: f(s(X),c()) -> f(X,c())
r4: f(c(),c()) -> f(a(),a())

The estimated dependency graph contains the following SCCs:

  {p3}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(s(X),c()) -> f#(X,c())

and R consists of:

r1: f(a(),a()) -> f(a(),b())
r2: f(a(),b()) -> f(s(a()),c())
r3: f(s(X),c()) -> f(X,c())
r4: f(c(),c()) -> f(a(),a())

The set of usable rules consists of

  (no rules)

Take the reduction pair:

  lexicographic combination of reduction pairs:
  
    1. lexicographic path order with precedence:
    
      precedence:
      
        c > s > f#
      
      argument filter:
    
        pi(f#) = 1
        pi(s) = [1]
        pi(c) = []
    
    2. lexicographic path order with precedence:
    
      precedence:
      
        c > s > f#
      
      argument filter:
    
        pi(f#) = 1
        pi(s) = [1]
        pi(c) = []
    
    3. lexicographic path order with precedence:
    
      precedence:
      
        c > s > f#
      
      argument filter:
    
        pi(f#) = 1
        pi(s) = [1]
        pi(c) = []
    

The next rules are strictly ordered:

  p1

We remove them from the problem.  Then no dependency pair remains.