cannot understand the approach…
would be grateful if someone could help me out in this problem
Let us assume that we have a set of m points such that no two lines passing through them are parallel.
Since, between each pair of m points, \exists a unique line, \therefore total number of lines, M = m \choose 2.
And, since no two lines are parallel, they intersect at exactly one point \therefore total number of points = M \choose 2
But, we have counted some points more than once.
From the figure, we can see that from each of the m points, (m-1) lines pass. If this wasn’t the case then these (m-1) lines would have added m-1 \choose 2 points, but they didn’t.
Thus, we have to remove these points from our answer.
So, the answer becomes M \choose 2 $-\ m \times\
m-1\choose 2$ which reduces to
\dfrac{m(m-1)(m-2)(m-3)}{8}
Here is the accepted code in Python.
[https://www.codechef.com/viewsolution/15264997][1]
[1]: https://www.codechef.com/viewsolution/15264997
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why are u multiplying (m-1)C(2)…couldn’t understand…pls elaborate