67 lines
1.9 KiB
Java
67 lines
1.9 KiB
Java
|
|
||
|
|
|
||
|
|
import edu.princeton.cs.introcs.StdOut;
|
||
|
|
import edu.princeton.cs.introcs.StdRandom;
|
||
|
|
|
||
|
|
/*************************************************************************
|
||
|
|
* Compilation: javac DoublingTest.java
|
||
|
|
* Execution: java DoublingTest
|
||
|
|
* Dependencies: ThreeSum.java Stopwatch.java StdRandom.java StdOut.java
|
||
|
|
*
|
||
|
|
* % java DoublingTest
|
||
|
|
* 250 0.0
|
||
|
|
* 500 0.0
|
||
|
|
* 1000 0.1
|
||
|
|
* 2000 0.6
|
||
|
|
* 4000 4.5
|
||
|
|
* 8000 35.7
|
||
|
|
* ...
|
||
|
|
*
|
||
|
|
*************************************************************************/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* The DoublingTest class provides a client for measuring
|
||
|
|
* the running time of a method using a doubling test.
|
||
|
|
*
|
||
|
|
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/14analysis">Section 1.4</a>
|
||
|
|
* of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
|
||
|
|
*
|
||
|
|
* @author Robert Sedgewick
|
||
|
|
* @author Kevin Wayne
|
||
|
|
*/
|
||
|
|
public class DoublingTest {
|
||
|
|
|
||
|
|
// This class should not be instantiated.
|
||
|
|
private DoublingTest() { }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns the amount of time to call ThreeSum.count() with N
|
||
|
|
* random 6-digit integers.
|
||
|
|
* @param N the number of integers
|
||
|
|
* @return amount of time (in seconds) to call ThreeSum.count()
|
||
|
|
* with N random 6-digit integers
|
||
|
|
*/
|
||
|
|
public static double timeTrial(int N) {
|
||
|
|
int MAX = 1000000;
|
||
|
|
int[] a = new int[N];
|
||
|
|
for (int i = 0; i < N; i++) {
|
||
|
|
a[i] = StdRandom.uniform(-MAX, MAX);
|
||
|
|
}
|
||
|
|
Stopwatch timer = new Stopwatch();
|
||
|
|
int cnt = ThreeSum.count(a);
|
||
|
|
return timer.elapsedTime();
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Prints table of running times to call ThreeSum.count()
|
||
|
|
* for arrays of size 250, 500, 1000, 2000, and so forth.
|
||
|
|
*/
|
||
|
|
public static void main(String[] args) {
|
||
|
|
for (int N = 250; true; N += N) {
|
||
|
|
double time = timeTrial(N);
|
||
|
|
StdOut.printf("%7d %5.1f\n", N, time);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|