Given a string, find the shortest substring containing all the characters of the string

The problem is an algorithmic question on the two side of the Pea pod, similar to some of the Leetcode's topics. The idea is this.

1. First, iterate through the string to find out the number of different characters in the string
2. Save a list for each character, and record the index of the character that appears in the string
3. Records the first letter of the string to be evaluated start (initial value is 0), ending index end (initial value is length-1)
4. The index value of the first letter of the possible string to be recorded is Pstart (the initial value is 0)
5. Re-iterate the string with the current index
   
   1. Updates the number of characters that are not traversed, updating the list of indexes corresponding to the current character. If the Pstart character corresponds to a list length greater than 1, remove Pstart from the index list and add the Pstart to 1 and repeat the process
   2. If the character at index is the first occurrence, the number of remaining characters is reduced by one
   3. Update [start:end] to [Pstart:index] if the number of characters remaining is 0 o'clock and the substring [pstart:index] is shorter than [start:end]

6. return substring [start:end

   You will find [Start:end] for the string to be asked. You can draw on the paper.

 class solution {String Getshortestsubstring (StringStr) {if(Str==NULL||Str. Length () <=1) {return Str; }//Record the starting index of the target string    intStart =0, end =Str. Length ()-1;//Record The starting position of the target string    intPstart =0; Map<character, list<integer>> map =NewHashmap<character, list<integer>> (); for(int Index=0;Index<Str. Length ();Index+ +) {Map.put (Str. CharAt (Index),NULL); }intRemainingcharacter = Map.keyset (). Size (); for(inti =0; I <Str. Length (); i++) {Charc =Str. charAt (i);if(Map.get (c) = =NULL) {List List =NewLinkedlist<integer> ();        Map.put (c, list);      remainingcharacter--; } map.get (c). Add (i); while(Map.get (Str. CharAt (Pstart)). Size () >1) {Map.get (Str. CharAt (Pstart)). Remove (0);      pstart++; }if(Remainingcharacter = =0) {if(I-pstart < End-start)          {start = Pstart;        end = i; }      }    }return Str. substring (start, end +1); }} class testsolution {@Test Public voidTestgetshortestsubstring () {Solution solution =NewSolution (); Assert.assertequals ("DBCCAAABCEFG", Solution.getshortestsubstring ("ABCDDBCCAAABCEFGGF")); }}

Given a string, find the shortest substring containing all the characters of the string