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I have a
List<string>
with 1500 strings. I am now using the following code to pull out only string that start with the string prefixText.
foreach(string a in <MYLIST>)
{
if(a.StartsWith(prefixText, true, null))
{
newlist.Add(a);
}
}
This is pretty fast, but I'm looking for google fast. Now my question is if I arrange the List in alphabetical order, then compare char by char can I make this faster? Or any other suggestions on making this faster?
640
The startsWith() method returns true if a string starts with a specified string. Otherwise it returns false . The startsWith() method is case sensitive. See also the endsWith() method.
Python example code use str. startswith() to find it a string starts with some string in a list. In the example list of substrings has converted into a tuple using tuple(list) in order to return a boolean if str contains substrings found it.
Python Find String in List using count() We can also use count() function to get the number of occurrences of a string in the list. If its output is 0, then it means that string is not present in the list. l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C'] s = 'A' count = l1.
The startswith() method returns True if a string starts with the specified prefix(string). If not, it returns False .
Thus 1500 is not really a huge number binary search on sorted list would be enough probably. Nevertheless most efficient algorithms for prefix search are based on the data structure named Trie or Prefix Tree. See: http://en.wikipedia.org/wiki/Trie
Following picture demonstrates the idea very briefly:
For c# implementation see for instance .NET DATA STRUCTURES FOR PREFIX STRING SEARCH AND SUBSTRING (INFIX) SEARCH TO IMPLEMENT AUTO-COMPLETION AND INTELLI-SENSE
61
You can use PLINQ (Parallel LINQ) to make the execution faster:
var newList = list.AsParallel().Where(x => x.StartsWith(prefixText)).ToList()
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