class Solution {
public:
    vector<int> replaceElements(vector<int>& arr) {
    // O(N) Time Complexity , O(1) Space complexity
      int n = arr.size();
      int maxSoFar = arr[n-1];
      arr[n-1] = -1;
      
      for(int i=n-2;i>=0;i--)
      {
        int temp = maxSoFar;
        if(maxSoFar < arr[i]) maxSoFar = arr[i];
        arr[i] = temp;
      }
      return arr;
    }
};