Easy O(n) approach with HashMaps

#1 
vector<int> Solution::solve(vector<int> &A)
{
    unordered_map<int,int>m;
    for(int i=0;i<A.size();i++)
    {
        if(m.find(A[i])!=m.end())
        {
            int index=m[A[i]];
            A[index]++;
            m[A[index]]=index;
        }
        m[A[i]]=i;
    }
    return A;
}