Max Stock Profit 3 - HJ

class Solution {
public:
    int maxProfit(vector<int>& prices) {
      if(prices.empty())    return 0;
      int minSoFar = prices[0];
      vector<int> arr1(prices.size());
      arr1[0] = 0;
      for(int i=1; i<prices.size(); i++){
        arr1[i] = max(arr1[i-1], prices[i] - minSoFar); //arr1[i] = max profit we can have by ending our transaction on day i-1, or by selling the stock on day i.. we take max of it...
        minSoFar = min(minSoFar, prices[i]);
      }

      int answer = 0;
      int maxSoFar = prices[prices.size()-1];
      for(int j=prices.size()-2; j>=0; j--){
        if(j==0){
            answer = max(maxSoFar-prices[j], answer);
            break;
        }
        answer = max(maxSoFar-prices[j] + arr1[j-1], answer);
        maxSoFar = max(maxSoFar, prices[j]);
      }


      return answer;


    }
};