Percolation/Site percolation: Difference between revisions
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=={{header|Java}}==
<syntaxhighlight lang="java">
import java.util.concurrent.ThreadLocalRandom;
public final class PercolationSiteSecond {
public static void main(String[] aArgs) {
final int rowCount = 15;
final int colCount = 15;
final int testCount = 1_000;
Grid grid = new Grid(rowCount, colCount, 0.5);
grid.percolate();
grid.display();
System.out.println("Proportion of " + testCount + " tests that percolate through the grid:");
for ( double probable = 0.0; probable <= 1.0; probable += 0.1 ) {
int percolationCount = 0;
for ( int test = 0; test < testCount; test++) {
Grid testGrid = new Grid(rowCount, colCount, probable);
if ( testGrid.percolate() ) {
percolationCount += 1;
}
}
double percolationProportion = (double) percolationCount / testCount;
System.out.println(String.format("%s%.1f%s%.4f", " p = ", probable, ": ", percolationProportion));
}
}
}
final class Grid {
public Grid(int aRowCount, int aColCount, double aProbability) {
createGrid(aRowCount, aColCount, aProbability);
}
public boolean percolate() {
for ( int x = 0; x < table[0].length; x++ ) {
if ( pathExists(x, 0) ) {
return true;
}
}
return false;
}
public void display() {
for ( int col = 0; col < table.length; col++ ) {
for ( int row = 0; row < table[0].length; row++ ) {
System.out.print(" " + table[col][row]);
}
System.out.println();
}
System.out.println();
}
private boolean pathExists(int aX, int aY) {
if ( aY < 0 || aX < 0 || aX >= table[0].length || table[aY][aX].compareTo(FILLED) != 0 ) {
return false;
}
table[aY][aX] = PATH;
if ( aY == table.length - 1 ) {
return true;
}
return pathExists(aX, aY + 1) || pathExists(aX + 1, aY) || pathExists(aX - 1, aY) || pathExists(aX, aY - 1);
}
private void createGrid(int aRowCount, int aColCount, double aProbability) {
table = new String[aRowCount][aColCount];
for ( int col = 0; col < aRowCount; col++ ) {
for ( int row = 0; row < aColCount; row++ ) {
table[col][row] = ( RANDOM.nextFloat(1.0F) < aProbability ) ? FILLED: EMPTY;
}
}
}
private String[][] table;
private static final String EMPTY = " ";
private static final String FILLED = ".";
private static final String PATH = "#";
private static final ThreadLocalRandom RANDOM = ThreadLocalRandom.current();
}
</syntaxhighlight>
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Proportion of 1000 tests that percolate through the grid:
p = 0.0: 0.0000
p = 0.1: 0.0000
p = 0.2: 0.0000
p = 0.3: 0.0000
p = 0.4: 0.0060
p = 0.5: 0.1040
p = 0.6: 0.5670
p = 0.7: 0.9480
p = 0.8: 1.0000
p = 0.9: 1.0000
p = 1.0: 1.0000
</pre>
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