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/*************************************************************************

* Compilation: javac RandomSurferHistogram.java

* Execution: java RandomSurferHistogram T

* Data files: http://introcs.cs.princeton.edu/16pagerank/tiny.txt

* http://introcs.cs.princeton.edu/16pagerank/medium.txt

* % java Transition < tiny.txt | java RandomSurferHistogram 1000000

* 0.27297 0.26583 0.14598 0.24729 0.06793

*************************************************************************/

public class RandomSurferHistogram {

public static void main(String[] args) {

int T = Integer.parseInt(args[0]); // number of moves

int N = StdIn.readInt(); // number of pages

StdIn.readInt(); // ignore integer required by input format

// Read transition matrix.

double[][] p = new double[N][N]; // p[i][j] = prob. that surfer moves from page i to page j

for (int i = 0; i < N; i++)

for (int j = 0; j < N; j++)

p[i][j] = StdIn.readDouble();

int[] freq = new int[N]; // freq[i] = # times surfer hits page i

// Start at page 0.

int page = 0;

for (int t = 0; t < T; t++) {

// Make one random move.

double r = Math.random();

double sum = 0.0;

for (int j = 0; j < N; j++)

{

// Find interval containing r.

sum += p[page][j];

if (r < sum) { page = j; break; }

}

freq[page]++;

// plot histogram of frequencies

StdDraw.clear();

StdDraw.setXscale(-1, N);

StdDraw.setYscale(0, t);

for (int k = 0; k < N; k++) {

StdDraw.filledRectangle(k, freq[k]/2.0, 0.25, freq[k]/2.0);

}

StdDraw.show(20);

}

// Print page ranks.

for (int i = 0; i < N; i++) {

StdOut.printf("%8.5f", (double) freq[i] / T);

}

StdOut.println();

}

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