-
Notifications
You must be signed in to change notification settings - Fork 1
/
Best_309.java
46 lines (41 loc) · 1.81 KB
/
Best_309.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
import java.util.Arrays;
import java.util.Collections;
public class Best_309 {
// https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/discuss/75931/Easiest-JAVA-solution-with-explanations
/*
buy[i]: Max profit till index i. The series of transaction is ending with a buy.
sell[i]: Max profit till index i. The series of transaction is ending with a sell.
buy[i] = Math.max(buy[i - 1], sell[i - 2] - prices[i]);
sell[i] = Math.max(sell[i - 1], buy[i - 1] + prices[i]);
Let b1, b0 represent buy[i - 1], buy[i]
Let s2, s1, s0 represent sell[i - 2], sell[i - 1], sell[i]
*/
public int maxProfit(int[] prices) {
if (prices == null || prices.length < 2)
return 0;
int b0, s0 = 0;
int b1 = -prices[0];
int s1 = 0, s2 = 0;
for (int price : prices) {
b0 = Math.max(b1, s2 - price);
s0 = Math.max(s1, b1 + price);
b1 = b0;
s2 = s1;
s1 = s0;
}
return s0;
}
// Another solution worth reading
// https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/discuss/75928/Share-my-DP-solution-(By-State-Machine-Thinking)
// This solution defines three states for any action sequence: Sell, Buy, Rest
// Let s, b, n denote sell, buy, no action
// If a sequence ends like {.....s}, it ends in Sell state
// If a sequence ends like {.....s, n, n}, it ends in Rest state
// If a sequence ends like {.....b}, it ends in Buy state
// If a sequence ends like {.....b, n, n}, it is also regarded as ending in Buy state
public static void main(String[] args) {
Best_309 test = new Best_309();
int[] testPrices = {6,1,3,2,4,7};
System.out.println(test.maxProfit(testPrices));
}
}