## Sunday, July 3, 2016

### [CareerCup] 11.8 The Rank of Number

[CareerCup] 11.8 The Rank of Number 数的排行 - Grandyang - 博客园
http://blog.csdn.net/fightforyourdream/article/details/17066125
11.8 Imagine you are reading in a stream of integers. Periodically, you wish to be able to look up the rank of a number x (the number of values less than or equal tox). Implement the data structures and algorithms to support these operations.That is, implement the method track(int x), which is called when each number is generated, and the method getRankOfNumber(int x), which returns the number of values less than or equal to x (not including x itself).
EXAMPLE
Stream (in order of appearance): 5, 1, 4, 4, 5, 9, 7, 13, 3
getRankOfNumber(l) = 0
getRankOfNumber(3) = 1
getRankOfNumber(4) = 3

```          20(4)
/       \
/         \
15(3)       25(2)
/          /
/          /
10(1)      23(0)
/  \         \
/    \         \
5(0)    13(0)    24(0)```

Note how we've handled the case in which d is not found in the tree. We check for the -1 return value, and, when we find it, return -1 up the tree. It is important that you handle cases like this.
RankNode root = null;

void track(int number) {
if (root == null) {
root = new RankNode(number);
} else {
root.insert(number);
}
}

int getRankOfNumber(int number) {
return root.getRank(number);
}

public class RankNode {
public int left_size = 0;
public RankNode left, right;
public int data = 0;
public RankNode(int d) {
data = d;
}

public void insert(int d) {
if (d <= data) {
if (left != null) left.insert(d);
else left= new RankNode(d);
left_size++;
} else {
if (right != null) right.insert(d);
else right = new RankNode(d);
}
}
public int getRank(int ct) {
if (d == data) {
return left_size;
} else if (d < data) {
if (left == null) return -1;
else return left.getRank(d);
} else {
int right_rank = right == null ? -1 : right.getRank(d);
if (right_rank == -1) return -1;
else return left_size + 1 + right_rank;
}
}
}