ruby - function that returns the number of letters that repeat in a string -

trying make function counts number of letters appear more once anywhere in string (not together, , not the number of times repeat). have:

def num_repeats(string)      repeat = []      i1 = 0     i2 = 1     while i1 < string.length          while  i2 < string.length             if (string[i1] == string[i2]) && (!repeat.include? string[i1])                  repeat << string[i1]             end             i2 +=1         end          i1+=1     end      return repeat.length end  puts(num_repeats('sldhelanlaskjkajksda')) 

for reason, pushes first letter of string if first letter has been used in rest of string, after that, seems method stops looping through rest of string.

i'd know first why current code not working , if there way fix it, , welcome other better solutions.

here orthodox way it:

'sldhelanlaskjkajksda'.each_char.group_by(&:itself).count{|_, v| v.length > 1} # => 6 

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reason code not work because, (i) once i2 loop terminates, increment i1, , try i2 loop in next i1 iteration, since i2 hasn't been touched after failed satisfy loop condition, not satisfy condition again, , i2 loop never run again, , (ii) initializing i2 constant.

to fix it, initialize i2 within i1 loop @ beginning, , initialize i2 = i1 + 1, not 1.