| Methods Summary |
|---|
| public static long | factorial1(int n)
if (n < 2) return 1L;
else return n*factorial1(n-1);
|
| public static long | factorial1a(int n)
if (n < 2) return 1L;
else return factorial1b(n, 1L);
|
| public static long | factorial1b(int n, long result)
//No need to consider n < 2, as factorial1a handles that
if (n == 2) return 2L*result;
else return factorial1b(n-1, result*n);
|
| public static long | factorial1c(int n, long result)
// if (n < 2) return 1L;
//else
if (n == 2) return 2L*result;
else return factorial1c(n-1, result*n);
|
| public static long | factorial2(int n)
long result = 1;
while(n>1)
{
result *= n--;
}
return result;
|
| public static long | factorial3(int n)
if (n < 2) return 1L;
else if (n < 15)
{
if (factorial3Cache[n] == 0)
factorial3Cache[n] = n*factorial3(n-1);
return factorial3Cache[n];
}
else return n*factorial3(n-1);
|
| public static long | factorial4(int n)
if (n < 15)
return factorial4Cache[n];
else return n*factorial4(n-1);
|
| public static long | factorial5(int n)
if (n < 2) return 1L;
else if (n < 21)
{
if (factorial5Cache[n] == 0)
factorial5Cache[n] = n*factorial2(n-1);
return factorial5Cache[n];
}
else return n*factorial2(n-1);
|
| public static void | main(java.lang.String[] args)
maintest(args);
if (args.length > 1)
maintest(args);
|
| public static void | maintest(java.lang.String[] args)
int REPEAT = Integer.parseInt(args[0]);
long res;
long time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial1(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial1 took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial1a(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial1a took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial1c(20, 1L);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial1c took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial2(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial2 took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial3(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial3 took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial4(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial4 took " + time);
time = System.currentTimeMillis();
for (int i = REPEAT; i > 0 ; i--)
{
res = factorial5(20);
if (res != FACTORIAL20)
System.out.println("oh dear: " + res);
}
time = System.currentTimeMillis() - time;
System.out.println("factorial5 took " + time);
|
