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Best_123.java
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Best_123.java
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public class Best_123 {
public static int maxProfit(int[] prices) {
// p1 = max(-x)
// p2 = max(-x+y)
// p3 = max(-x+y-z)
// p4 = max(-x+y-z+w)
int p1 = Integer.MIN_VALUE, p3 = Integer.MIN_VALUE;
int p2 = 0, p4 = 0;
for (int i:prices) {
p1 = Math.max(p1, -i);
p2 = Math.max(p2, p1+i);
p3 = Math.max(p3, p2-i);
p4 = Math.max(p4, p3+i);
}
return p4;
}
// Print optimal strategy
/*
public int maxProfit(int[] prices) {
int p1 = Integer.MIN_VALUE;
int p2 = 0;
int p3 = Integer.MIN_VALUE;
int p4 = 0;
Tuple t1 = new Tuple();
Tuple t2 = new Tuple();
Tuple t3 = new Tuple();
Tuple t4 = new Tuple();
for (int i = 0; i < prices.length; i++) {
int p = prices[i];
if (-p > p1) {
p1 = -p;
t1 = new Tuple(i);
}
if (p1 + p > p2) {
p2 = p1 + p;
t2 = new Tuple(t1.a, i);
}
if (p2 - p > p3) {
p3 = p2 - p;
t3 = new Tuple(t2.a, t2.b, i);
}
if (p3 + p > p4) {
p4 = p3 + p;
t4 = new Tuple(t3.a, t3.b, t3.c, i);
}
}
System.out.println("buy on: " + t4.a);
System.out.println("sell on: " + t4.b);
System.out.println("buy on: " + t4.c);
System.out.println("sell on: " + t4.d);
return p4;
}
class Tuple {
int a, b, c, d;
Tuple() {
a = b = c = d = -1;
}
Tuple(int a) {
this.a = a;
}
Tuple(int a, int b) {
this.a = a;
this.b = b;
}
Tuple(int a, int b, int c) {
this.a = a;
this.b = b;
this.c = c;
}
Tuple(int a, int b, int c, int d) {
this.a = a;
this.b = b;
this.c = c;
this.d = d;
}
}
*/
public static void main (String args[]) {
int[] testPrices = {1,4,2,1};
System.out.println(maxProfit(testPrices));
}
}