MapSumPairs

class MapSum {
    
    Map<String,Integer> map;
    Map<String,Integer> score;
    

    /** Initialize your data structure here. */
    public MapSum() {
        map = new HashMap();
        score = new HashMap();
    }
    
    public void insert(String key, int val) {
        
        int delta = val - map.getOrDefault(key,0);
        map.put(key,val);
        String prefix="";
        for(char c:key.toCharArray())
        {
            prefix+=c;
            score.put(prefix, score.getOrDefault(prefix,0)+delta);
        }
        
    }
    
    public int sum(String prefix) {
        return score.getOrDefault(prefix,score.getOrDefault(prefix,0));
    }
}

/**
 * Your MapSum object will be instantiated and called as such:
 * MapSum obj = new MapSum();
 * obj.insert(key,val);
 * int param_2 = obj.sum(prefix);
 */