1282. Group the People Given the Group Size They Belong To

class Solution {
    public List<List<Integer>> groupThePeople(int[] groupSizes) {
        ArrayList<List<Integer>> ans = new ArrayList<>();
        HashMap<Integer, ArrayList<Integer>> map = new HashMap<>(); //map(groupsize, id's list)
        for(int i=0;i<groupSizes.length;i++){
            if(!map.containsKey(groupSizes[i])){
                map.put(groupSizes[i], new ArrayList<>());
            }
            ArrayList<Integer> currGroup = map.get(groupSizes[i]);//retireves the arraylist associated witht he current groupsize
            currGroup.add(i);
            if(currGroup.size()==groupSizes[i]){
                ans.add(currGroup);
                map.remove(groupSizes[i]);
            }
        }
        return ans;
    }
}

/*
LOGIC---
JUST DO WHAT THE QUESTION SAY
TC-O(n)
SC-O(n)
*/