YES

We show the termination of the TRS R:

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

-- SCC decomposition.

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

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

and R consists of:

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

The estimated dependency graph contains the following SCCs:

  {p2}
  {p1}


-- Reduction pair.

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

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

and R consists of:

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

The set of usable rules consists of

  (no rules)

Take the monotone reduction pair:

  lexicographic combination of reduction pairs:
  
    1. lexicographic path order with precedence:
    
      precedence:
      
        s > c > f#
      
      argument filter:
    
        pi(f#) = [1, 2]
        pi(c) = [1]
        pi(s) = 1
    
    2. matrix interpretations:
    
      carrier: N^1
      order: standard order
      interpretations:
        f#_A(x1,x2) = x1 + x2
        c_A(x1) = x1 + 1
        s_A(x1) = x1 + 2
    

The next rules are strictly ordered:

  p1
  r1, r2, r3

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

-- Reduction pair.

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

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

and R consists of:

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

The set of usable rules consists of

  (no rules)

Take the monotone reduction pair:

  lexicographic combination of reduction pairs:
  
    1. lexicographic path order with precedence:
    
      precedence:
      
        a > s > f#
      
      argument filter:
    
        pi(f#) = [1, 2]
        pi(s) = [1]
        pi(a) = 1
    
    2. matrix interpretations:
    
      carrier: N^1
      order: standard order
      interpretations:
        f#_A(x1,x2) = x1 + x2
        s_A(x1) = x1 + 1
        a_A(x1) = x1 + 2
    

The next rules are strictly ordered:

  p1
  r1, r2, r3

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