Leetcode Problem 1830. Minimum Number of Operations to Make String Sorted

1830. Minimum Number of Operations to Make String Sorted

Leetcode Solutions

Calculating Lexicographic Rank with Factorials and Inverse Modulo

  1. Initialize a count array cnt of size 26 to zero, representing the count of each character from 'a' to 'z'.
  2. Initialize variables ans and tot to zero, and comb_tot to one.
  3. Iterate over the string s in reverse.
  4. Convert the current character to its corresponding index num (0 for 'a', 1 for 'b', etc.).
  5. Update the count array cnt for the current character.
  6. Increment tot to keep track of the total number of characters processed so far.
  7. Update comb_tot by multiplying with tot and dividing by the count of the current character.
  8. Calculate the sum of counts of characters smaller than the current character.
  9. Update ans by adding the product of comb_tot and the sum of counts of smaller characters, divided by tot.
  10. Return ans modulo 1,000,000,007.
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Brute Force Simulation of Operations

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