22.用户分组

class Solution {
public:
    vector<vector<int>> groupThePeople(vector<int>& gr) {
        vector<vector<int>>ans,ret;
        ans.resize(gr.size()+1);
        ans[gr[0]].push_back(0);
        for(int i=1;i<gr.size();i++){
            ans[gr[i]].push_back(i);
        }
        for(int i=0;i<ans.size();i++){
            if(ans[i].empty())continue;
            if(ans[i].size()>i){
                for(int j=0;j<ans[i].size();j+=i){
                    vector<int>v(ans[i].begin()+j,ans[i].begin()+i>=ans[i].end()?ans[i].end():ans[i].begin()+j+i);
                    ret.push_back(v);
                }
            }
            else ret.push_back(ans[i]);
        }
        return ret;
    }
};