Let's say that I have an array of doubles, for example double[] foo = double[] {1.3, 4.5, 8.12, 10.1};
Just assume the doubles are in increasing order.
Can you guys make me a fast algorithm (function) that takes two parameters, a double array and a double, and returns the lowest element in the array that is greater than or equal to that given double? By lowest element, I actually mean the "index of the lowest element".
Phrased more clearly: Let a_0, a_1, ..., a_n be positive real numbers. Let a be a positive real number. Find the least i such that a_i >= a.
Is there any faster way to do this than just for-looping through the array?
Notice that the beast should be fast in the sense that the array is constant throughout, but the double (that I call a above) is changing alot and I will always need to find such a "least index" for different a's loads of times over and over again.
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I would convert to a List<double> using the array.ToList() command or start out using a list. I would then use the List.Sort() command and then iterate through the List until you find the first one that it greater than your number. Then break out of the loop as you found what you are looking for. This way you don't have to iterate through the entire sequence of numbers.
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by: jaime_olivaresPosted on 2008-07-21 at 05:29:44ID: 22049775
You need to do a binary search, it is the fastest way to search an ordered array. .net library provides a BinarySearch method for an Array object, but in this case you have to do by yourself, since your are not looking for an specific array element, but an element with a near value.