如何压缩 C 中字符串中的连续重复元素？

Question

An example of my problem:

input: "abcabcabcabcxyxyxyccccccc"

output: "abc4xy3c7"

So far, I've made a code that can count all the charaters in the string and store those numbers into an array from 0 to 25, which represents the alphabet (I'm only considering small letters). For the example above, my code would generate the following array:

letter_count = [4 4 4 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 3 0]

From this, I'd be able to know which substrings are which and print them accordingly. But I can't do it, no matter how I try.

Could someone help me?

Answer 1

Update: removing steps to convert to array

I assume you are starting off with a string so...

The first initialize an empty auxiliary array which will hold the result

Next cycle through the string like an array asking if the current element is the same as the last element in your results array, if not then add the current element to the auxiliary array else continue to next element.

This should give you what you are looking for.

Answer 2

This sounds a bit home-worky so I'll just put my thoughts down here. The letter_count array has no value here. I think the approach to use is:-

startindex = 0
while startindex < length of string
  for n = 1 to (length of string - startindex) / 2
    if substring (startindex, n) == substring (startindex+n, n) then
      found a repitition, count how many times substring is repeated
      output substring and repitition count
      set startindex to index of last character in repeated string
      break
  startindex = startindex + 1

There's a few things missing (if you find a non-repeated sequence like abcdcd for example) but it's a start I guess.

Thinking about the problem, what would the output for ababcdababcd be? Would it be ab2cd1ab2cd1 or ababcd2? Should the algorithm find the shortest compacted string?