A Rainbow $k$-Matching in the Complete Graph with $r$ Colors

An $r$-edge-coloring of a graph is an assignment of $r$ colors to the edges of the graph. An exactly $r$-edge-coloring of a graph is an $r$-edge-coloring of the graph that uses all $r$ colors. A matching of an edge-colored graph is called rainbow matching , if no two edges have the same color in the matching. In this paper, we prove that an exactly $r$-edge-colored complete graph of order $n$ has a rainbow matching of size $k(\ge 2)$ if $r \ge max\{{2k-3\choose 2}+2, {k-2\choose 2}+(k-2)(n-k+2)+2 \}$, $k \ge 2$, and $n \ge 2k+1$. The bound on $r$ is best possible.