  The combinatorial R matrices are obtained for a family {B_l} of crystals for
U'_q(C^{(1)}_n) and U'_q(A^{(2)}_{2n-1}), where B_l is the crystal of the
irreducible module corresponding to the one-row Young diagram of length l. The
isomorphism B_l\otimes B_k \simeq B_k \otimes B_l and the energy function are
described explicitly in terms of a C_n-analogue of the Robinson-Schensted-Knuth
type insertion algorithm. As an application a C^{(1)}_n-analogue of the Kostka
polynomials is calculated for several cases.
