Fastest way to "ignore" elements from array without removal

[z]

What would be the overall best manner(in ease of implementation 
and speed) to arbitrarily remove an item in the middle of an 
array while iterating through it?
So far i've thought about simply using D's standard [0...x] ~ 
[x+1..$] with an array of indexes but wouldn't that just cause 
slow reallocations? According to wikipedia the performance would 
be suboptimal.[1]
I've also thought about using a pointer array and just assigning 
a null pointer when the item doesn't need to be iterated on but 
i'm not sure which method will result in the fastest execution 
times for the general case where over half of the items will be 
removed from the index/pointer array.

Big thanks

[1] - https://en.wikipedia.org/wiki/Dynamic_array#Performance