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Program to perform string compression in Python

Suppose we have a string s. We have to compress this string into Run length encoding form. So when a character is repeated k number of times consecutively like 'bbbb' here letter 'b' is repeated four times consecutively, so the encoded form will be 'b4'. For single characters we shall not add the count into it.

So, if the input is like s = "abbbaaaaaaccdaaab", then the output will be ab3a6c2da3b

To solve this, we will follow these steps −

  • res := blank string
  • cnt := 1
  • for i in range 1 to size of s - 1, do
    • if s[i - 1] is same as s[i], then
      • cnt := cnt + 1
    • otherwise,
      • res := res concatenate s[i - 1]
      • if cnt > 1, then
        • res := res concatenate cnt
      • cnt := 1
  • res := res + last character of s
  • if cnt > 1, then
    • res := res concatenate cnt
  • return res

Example

Let us see the following implementation to get better understanding −

def solve(s):
   res = ""
   cnt = 1
   for i in range(1, len(s)):
      if s[i - 1] == s[i]:
         cnt += 1
      else:
         res = res + s[i - 1]
         if cnt > 1:
            res += str(cnt)
         cnt = 1
   res = res + s[-1]
   if cnt > 1:
      res += str(cnt)
   return res

s = "abbbaaaaaaccdaaab"
print(solve(s))

Input

"abbbaaaaaaccdaaab"

Output

ab3a6c2da3b