In order to illustrate the basic ideas, this section describes an implementation of M-way search trees in main memory. According to Definition , each internal node of an M-way search tree has n subtrees, where n is at least two and at most M. Furthermore, if a node has n subtrees, it must contain n-1 keys.
Figure shows how we can implement a single node of an M-way search tree. The idea is that we use two arrays in each node--the first holds the keys and the second contains pointers to the subtrees. Since there are at most M-1 keys and M subtrees, the first array is one element shorter than the second array.
Figure: Representing a Node of an M-Way Search Tree