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BestTimeToBuyNSellStocks_withTransactionFee.java
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BestTimeToBuyNSellStocks_withTransactionFee.java
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package Dynamic_Programming;
import java.util.Arrays;
public class BestTimeToBuyNSellStocks_withTransactionFee {
// Tabulation
public int maxProfit(int[] prices, int fee) {
int n = prices.length;
int[][] dp = new int[n+1][2];
int profit = 0;
for (int i=n-1; i>=0; i--){
for (int buy=0; buy<=1; buy++){
// i can buy -> buy == 0
if (buy == 0){
int op1 = -prices[i] + dp[i+1][1];
int op2 = 0 + dp[i+1][0];
profit = Math.max(op1, op2);
}
// i can NOT buy -> buy == 1
if (buy == 1){
int op1 = prices[i] + dp[i+1][0];
// process completed
op1 = op1 - fee;
int op2 = 0 + dp[i+1][1];
profit = Math.max(op1, op2);
}
dp[i][buy] = profit;
}
}
return dp[0][0];
}
// Memoization
public static int solveMemo(int[] prices, int fee){
int n = prices.length;
int[][] dp = new int[n][2];
for (int i=0; i<n; i++){
Arrays.fill(dp[i], -1);
}
return helper(0, 1, prices, dp, n, fee);
}
public static int helper(int ind, int buy, int[] prices, int[][] dp, int n, int fee){
// base case
if (ind >= n) return 0;
if (dp[ind][buy] != -1) return dp[ind][buy];
// i can buy
if (buy == 1){
int op1 = -prices[ind] + helper(ind+1, 0, prices, dp, n, fee);
int op2 = 0 + helper(ind+1, 1, prices, dp, n, fee);
return dp[ind][buy] = Math.max(op1, op2);
}else {
// i can not buy
// cool down of just after -> ind + 2
int op1 = prices[ind] + helper(ind+1, 1, prices, dp, n, fee);
// process completed
op1 = op1 - fee;
int op2 = 0 + helper(ind+1, 0, prices, dp, n, fee);
return dp[ind][buy] = Math.max(op1, op2);
}
}
public static void main(String[] args) {
int[] prices = {1,3,2,8,4,9};
int fee = 2;
System.out.println(solveMemo(prices, fee));
}
}