What is Interval

A pair of integers [ a , b ] where b denotes the rank of v in a post-order traversal of a trie. Here the ranks are assumed to begin with 1, and all the children of a node are assumed to be ordered and fixed during the traversal. In addition, a denotes the lowest rank for any node u in the subtree rooted at v . Its purpose is to check the reachability. Let [ a , b ] an [ c , d ] be the intervals associated with v and u , respectively. If [ c , d ] ? [ a , b ], then u is reachable from v through a path in the tree.

A musical interval is the difference between two pitches.

It may be written represented in the following manner: where and are lower and upper values of the interval respectively.