interview article code

Longest Substring Without Repeating Characters.java

public int lengthOfLongestSubstring(String s) {
    HashMap<Character,Integer> set = new HashMap<>();
    int max = 0;int j=0;
    for(int i=0;i<s.length();i++){
        char c = s.charAt(i);
        if(set.containsKey(c)){
            // as we dont delete history, we dont
            // want to jump back to index in a substring that is dead
            j = Math.max(j, set.get(c)+1); 
        }
        set.put(c,i);
        max = Math.max(i-j+1, max);

    }
    return max;
}