Question

I have this two string string1 and string2. What are my best option to check if string2 is present in string1. How do I implement in Ruby. Currently I am using Regex match.

Answer 1

1.9.3p194 :016 > Benchmark.measure{ 1_000_000.times{ 'asd'['a'] } }
 =>   0.430000   0.000000   0.430000 (  0.431638)

1.9.3p194 :017 > Benchmark.measure{ 1_000_000.times{ 'asd' =~ /a/ } }
 =>   0.420000   0.000000   0.420000 (  0.415391)

1.9.3p194 :018 > Benchmark.measure{ 1_000_000.times{ 'asd'.include? 'a' } }
 =>   0.340000   0.000000   0.340000 (  0.343843)

Surprisingly, count('a') > 0 is giving me good results:

1.9.3p194 :031 >   Benchmark.measure{ 10_000_000.times{ 'asd'.count('a') > 0 } }
 =>   3.100000   0.000000   3.100000 (  3.099447)

1.9.3p194 :032 > Benchmark.measure{ 10_000_000.times{ 'asd'.include?('a') } }
 =>   3.220000   0.000000   3.220000 (  3.226521)

But:

# count('a') > 0
1.9.3p194 :056 >   Benchmark.measure{ 10_000_000.times{ 'asdrsguoing93hafehbsefu3nr3wrbibaefiafb3uwfniw4ufnsbei'.count('a') > 0 } }
 =>   3.630000   0.000000   3.630000 (  3.633329)
# include?('a')
1.9.3p194 :057 > Benchmark.measure{ 10_000_000.times{ 'asdrsguoing93hafehbsefu3nr3wrbibaefiafb3uwfniw4ufnsbei'.include?('a') } }
 =>   3.220000   0.000000   3.220000 (  3.224986)
# =~ /a/
1.9.3p194 :058 > Benchmark.measure{ 10_000_000.times{ 'asdrsguoing93hafehbsefu3nr3wrbibaefiafb3uwfniw4ufnsbei' =~ /a/ } }
 =>   3.040000   0.000000   3.040000 (  3.043130)

So: talking strictly about performance, you should do a test considering the distribution of your strings (which rarely is random). Talking about expressivity, maybe include? is the best choice.