buy_stock_sell_3.cpp

#include<bits/stdc++.h>

using namespace std;
class Solution {
public:
    int solve(int ind, int buy, int cap, vector<int> prices, int n, vector<vector<vector<int>>> &dp){
        if(ind == n || cap == 0) return 0;

        if(dp[ind][buy][cap] != -1) return dp[ind][buy][cap];
        if(buy == 1){
            return dp[ind][buy][cap] = max(-prices[ind] + solve(ind + 1, 0, cap, prices, n, dp), 
                0 + solve(ind+1, 1, cap, prices, n, dp));
        }

        return dp[ind][buy][cap] = max(prices[ind] + solve(ind+1, 1, cap-1, prices, n, dp), 
                0 + solve(ind +1, 0, cap, prices, n, dp));

        
    }

    int maxProfit(vector<int>& prices) {
        int n = prices.size();
        vector<vector<vector<int>>> dp(n+1, vector<vector<int>>(2, vector<int>(3, 0)));

        for(int ind = n-1;ind >=0; ind--){
            for(int buy = 0;buy <=1;buy++){
                for(int cap = 1;cap <= 2;cap++){
                    if(buy == 1){
                        dp[ind][buy][cap] = max(-prices[ind] + dp[ind + 1][0][cap], 
                            0 + dp[ind+1][1][cap]);
                    }
                    else{
                         dp[ind][buy][cap] = max(prices[ind] + dp[ind+1][1][cap-1], 
                            0 + dp[ind +1][0][cap]);
                    }

       
                }
            }
        }
        return dp[0][1][2];
    }
};