Sword offer-Fifth chapter optimization of Time and space efficiency (the first occurrence of a tangent character in a string)

Title: The first occurrence of a tangent character in a string

Idea: Use HashMap to store the corresponding char value and the number of occurrences of the char. Make a variable once to get the first character that appears only once.

Java code:

ImportJava.util.LinkedHashMap;//idea: Use HashMap to store the corresponding char value and the number of occurrences of the char. Make a variable once to get the first character that appears only once.  Public classFirstnotrepeatingchar { PublicCharacter firstnotrepeating (String str) {if(str==NULL)            return NULL; Char[] chars=Str.tochararray (); Linkedhashmap<Character,Integer> hashmap=NewLinkedhashmap<character,integer>();  for(Charitem:chars) {            if(Hashmap.containskey (item)) Hashmap.put (item, Hashmap.get (item)+1); Elsehashmap.put (item,1); }         for(CharKey:hashMap.keySet ()) {            if(Hashmap.get (Key) ==1)                returnkey; }        return NULL; }     Public Static voidMain (string[] args) {String str= "ABACCDEBFF"; Firstnotrepeatingchar Test=NewFirstnotrepeatingchar ();    SYSTEM.OUT.PRINTLN (test.firstnotrepeating (str)); }}

Sword offer-Fifth chapter optimization of Time and space efficiency (the first occurrence of a tangent character in a string)