ValidAlienDictionary.java

class Solution {

    // TC : O(n2)
    // SC : O(1)
    public boolean isAlienSorted(String[] words, String order) {
        Map<Character, Integer> map = new HashMap<>();
        int weight = 1;
        for(char c: order.toCharArray()){
            map.put(c, weight);
            weight++;
        }

        for(int i=0;i<words.length -1;i++){
            String first = words[i];
            String second = words[i+1];
            if(!helper(first, second, map)){
                return false;
            }
        }

        return true;

    }

    private boolean helper(String s1, String s2, Map<Character, Integer> map){
        int i1=0;
        int i2=0;
        while(i1 <s1.length() && i2<s2.length()){
            if(s1.charAt(i1)!=s2.charAt(i2)){
                if(map.get(s1.charAt(i1))< map.get(s2.charAt(i2)) ){
                    return true;
                } else{
                    return false;
                }
            }
            i1++;
            i2++;
        }


        // s1 ="hello" s2 ="hell"
        if(s1.length()>s2.length()){
            return false;
        }
        return true;
    }
}