ZOJ Problem Set - 2967
Evelyn likes drawing very much. Today, she draws lots of rainbows on white paper of infinite size, each using a different color. Since there're too many rainbows now, she wonders, how many of them can be seen?
For simplicity, each rainbow Li is represented as a non-vertical line specified by the equation: y=aix+bi. A rainbow Li can be seen if there exists some x-coordinate x0 at which, its y-coordinate is strictly greater than y-coordinates of any other rainbows: aix0+bi > ajx0+bj for all j != i.
Now, your task is, given the set of rainbows drawn, figure out the number of rainbows that can be seen.
Standard input will contain multiple test cases. The first line of the input is a single integer T (1 <= T <= 60) which is the number of test cases. And it will be followed by T consecutive test cases.
There's a blank line before every case. In each test case, there will first be an integer n (1 <= n <= 5000), which is the number of rainbows. Then n consecutive real number pairs follow. Each pair contains two real numbers, ai and bi, representing rainbow Li: y=aix+bi. No two rainbows will be the same, that is to say, have the same a and b.
Results should be directed to standard output. The output of each test case should be a single integer, which is the number of rainbows that can be seen.Sample Input
2 1 1 1 3 1 0 2 0 3 0Sample Output
Author: DAI, Wenbin
Source: The 5th Zhejiang Provincial Collegiate Programming Contest