Update buy_sell_with_cooldown_dp.cpp

Author: avidLearnerInProgress

buy_sell_with_cooldown_dp.cpp

@@ -1,19 +1,53 @@
-//fsm based solution
+// //fsm based solution
+
+// class Solution {
+// private:
+//     const int STATE_NUM = 3, STEP_NUM = 2, S_BUY = 0, S_SELL = 1, S_COOL = 2;
+// public:
+//     int maxProfit(vector<int>& prices) {
+//         int state[STATE_NUM][STEP_NUM], i, j, steps = prices.size(),cur = 0, next = 1;
+        
+//         fill_n(&state[0][0], STATE_NUM*STEP_NUM, INT_MIN);
+        
+//         for(i=0,state[0][0]=0;i<steps;++i, swap(cur, next)) {
+//             state[S_BUY][next]  = max(state[S_BUY][cur], state[S_COOL][cur]);
+//             state[S_SELL][next] = max(state[S_BUY][cur]-prices[i], state[S_SELL][cur]);
+//             state[S_COOL][next] = state[S_SELL][cur] + prices[i];
+//         }
+//         return max(state[S_BUY][cur], state[S_COOL][cur]);
+//     }
+// };
+
 
 class Solution {
-private:
-    const int STATE_NUM = 3, STEP_NUM = 2, S_BUY = 0, S_SELL = 1, S_COOL = 2;
 public:
-    int maxProfit(vector<int>& prices) {
-        int state[STATE_NUM][STEP_NUM], i, j, steps = prices.size(),cur = 0, next = 1;
+    
+    int dp[50001][2][2];
+    int solve(vector<int> &prices, int cool, int own, int index) {
 
-        fill_n(&state[0][0], STATE_NUM*STEP_NUM, INT_MIN);
+        //basecase
+        if(index == prices.size()) 
+            return 0;
 
-        for(i=0,state[0][0]=0;i<steps;++i, swap(cur, next)) {
-            state[S_BUY][next]  = max(state[S_BUY][cur], state[S_COOL][cur]);
-            state[S_SELL][next] = max(state[S_BUY][cur]-prices[i], state[S_SELL][cur]);
-            state[S_COOL][next] = state[S_SELL][cur] + prices[i];
+        if(dp[index][own][cool] != -1) 
+            return dp[index][own][cool];
+        
+        if(own) {
+            int case1 = prices[index] + solve(prices, 1, 0, index + 1);
+            int case2 = solve(prices, 0, 1, index + 1);
+            return dp[index][own][cool] = max(case1, case2);
         }
-        return max(state[S_BUY][cur], state[S_COOL][cur]);
+        
+        else {   
+            int case1 = (cool == 1) ? 0 : (-prices[index] + solve(prices, 0, 1, index + 1));
+            int case2 = solve(prices, 0, 0, index + 1);
+            return dp[index][own][cool] = max(case1, case2);
+        }   
+    }
+    
+    int maxProfit(vector<int>& prices) {
+        memset(dp, -1, sizeof dp);
+        return solve(prices, 0, 0, 0);
+        
     }
 };