Leetcode Remove Duplicate Letters

The original title link is here: https://leetcode.com/problems/remove-duplicate-letters/

Topic:

Given a string which contains only lowercase letters, remove duplicate letters so this every letter appear once and only O nCE. You must make sure your result are the smallest in lexicographical order among all possible results.

Example:

Given"bcabc"
Return"abc"

Given"cbacdcbc"
Return"acdb"

Exercises

After the character, find the smallest string that matches the order of the original string.

Count is counted first for the number of the original char. Returns the position of the first char of a string with a PO. If you encounter S.charat (i) < S.charat (PO), update the PO to I.

The number of S.charat (i) corresponding to count is also reduced. When the quantity is 0, the only char that has just been lost is indicated. A char on the PO is the first char to return.

Recursively substring the back of the PO.

Time Complexity:o (n^2). Recursive call. N + (n-1) + ... + 1. Space:o (n).

AC Java:

1  Public classSolution {2      Publicstring Removeduplicateletters (string s) {3         if(s = =NULL|| S.length () = = 0){4             returns;5         }6         int[] Count =New int[26];7         intLen =s.length ();8          for(inti = 0; i<len; i++){9Count[s.charat (i)-' a ']++;Ten         } One         intPO = 0; A          for(inti = 0; i<len; i++){ -             if(S.charat (i) <S.charat (PO)) { -PO =i; the             } -Count[s.charat (i)-' a ']--; -             if(Count[s.charat (i)-' a '] = = 0) {//a unique value is lost, and char on the PO is the first char that returns a string -                  Break;  +             } -         } +          AString first =string.valueof (S.charat (PO)); at         returnFirst + removeduplicateletters (s.substring (po+1) replaceall (First, "")); -     } -}

Leetcode Remove Duplicate Letters