How can we randomly generate a set of m integers from an array of size n..Each element must have equal probability of being chosen..
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Название |
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m times pick random element from array and remove it. To do it in O(N log N), one can use segment tree.
UPD. Oops, my solution looks way overcomplicated :)
while (i<m)
{
1) choose a random number(0..n-1)
2) add a[random] to your set
3) swap (a[random], a[n-1])
4) n--, i++
}
This should take O(m)