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