11.8 data structures and algorithms support track and rank operations.

The track operation is similar to the insert operation.

The rank operation returns a number of smaller or equal elements than the current element.

 

Idea: track operation inserts and constructs BST (not guaranteed balance), but adds a leftsize to the node. Let's take a look here.

 

public class Solution {    private static RankNode root = null;    public static void track(int number) {        if (root == null) {            root = new RankNode(number);        } else {            root.insert(number);        }    }    public static int getRankOfNumber(int number) {        return root.getRank(number);    }    public static void main(String[] args) {        track(20);        track(15);        track(25);        track(10);        track(23);        track(5);        track(13);        track(24);        System.out.println(getRankOfNumber(20));        System.out.println(getRankOfNumber(15));        System.out.println(getRankOfNumber(8));    }}class RankNode {    int val;    int leftSize;    RankNode left;    RankNode right;    public RankNode(int v) {        val = v;    }    public void insert(int t) {        if (t <= val) {            if (left != null) {                left.insert(t);            } else {                left = new RankNode(t);            }            leftSize++;        } else {            if (right != null) {                right.insert(t);            } else {                right = new RankNode(t);            }        }    }    public int getRank(int t) {        if (t == val) {            return leftSize;        } else if (t < val) {            if (left == null)                return -1;            else                return left.getRank(t);        } else {            if (right == null)                return -1;            else {                return right.getRank(t) + leftSize + 1;            }        }    }}

 

11.8 data structures and algorithms support track and rank operations.