Solution without hashmap, O(n) complexity

  • 0
    public class Solution {
        public int lengthOfLongestSubstring(String s) {
            int[] index = new int[256];
            int max=0, size=0, base=0;
            for(int i=0; i<s.length(); i++){
                    index[s.charAt(i)] = i+1;
                        max = size;
                    size = i-index[s.charAt(i)]+1;
                    base = index[s.charAt(i)]+1;
                    index[s.charAt(i)] = i+1;
            return max;

    This code can solve this problem without using hash map.
    The idea is simple, using a base variable to track the start of string, and using an array index to track the last appearance of one character.

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