java - Code with minimum time complexity to find occurrence of max and min Character in a String -

i have find best possible solution find occurrence of min , max character in given string.

code using below

 string prefix="aaaaabbbbddddfeeeee"  hashmap<character, integer> alphabetcountmapinit = new hashmap<character, integer>();            //time complexity : o(n)  (char c : prefix.tochararray()) {             alphabetcountmapinit.put(c, alphabetcountmapinit.get(c) == null ? 1 : alphabetcountmapinit.get(c) + 1);           }       //time complexity :  o(n)   int minoccurence = collections.min(alphabetcountmapinit.values());   system.out.println(maxoccurance);    //time complexity :  o(n)   int maxoccurence = collections.max(alphabetcountmapinit.values());     system.out.println(minoccurance); 

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can suggest me solution more optimized in terms of time complexity, need iterate around 90^90 number of string records.?

you don't have use hashmap. there 26 letters, can use int[] count = new int[26]; count each letter. when have 10 as, set count['a' - 97] = 10 count[0] = 10. , @ same time, use int min = 0, max = 0;to keep track of min , max when iterate string , write count array. o(n) time , o(1) space.