Resistor mesh: Difference between revisions
Added Java
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In other words, each coordinate pair is matched up with the coordinate pair that you would get by adding the offset to the first of the pair. In actual use, we use this four times, with four offsets (two horizontal and two vertical) to get our complete mesh.
=={{header|Java}}==
{{trans|Kotlin}}
<lang Java>import java.util.ArrayList;
import java.util.List;
public class ResistorMesh {
private static final int S = 10;
private static class Node {
double v;
int fixed;
Node(double v, int fixed) {
this.v = v;
this.fixed = fixed;
}
}
private static void setBoundary(List<List<Node>> m) {
m.get(1).get(1).v = 1.0;
m.get(1).get(1).fixed = 1;
m.get(6).get(7).v = -1.0;
m.get(6).get(7).fixed = -1;
}
private static double calcDiff(List<List<Node>> m, List<List<Node>> d, int w, int h) {
double total = 0.0;
for (int i = 0; i < h; ++i) {
for (int j = 0; j < w; ++j) {
double v = 0.0;
int n = 0;
if (i > 0) {
v += m.get(i - 1).get(j).v;
n++;
}
if (j > 0) {
v += m.get(i).get(j - 1).v;
n++;
}
if (i + 1 < h) {
v += m.get(i + 1).get(j).v;
n++;
}
if (j + 1 < w) {
v += m.get(i).get(j + 1).v;
n++;
}
v = m.get(i).get(j).v - v / n;
d.get(i).get(j).v = v;
if (m.get(i).get(j).fixed == 0) {
total += v * v;
}
}
}
return total;
}
private static double iter(List<List<Node>> m, int w, int h) {
List<List<Node>> d = new ArrayList<>(h);
for (int i = 0; i < h; ++i) {
List<Node> t = new ArrayList<>(w);
for (int j = 0; j < w; ++j) {
t.add(new Node(0.0, 0));
}
d.add(t);
}
double[] cur = new double[3];
double diff = 1e10;
while (diff > 1e-24) {
setBoundary(m);
diff = calcDiff(m, d, w, h);
for (int i = 0; i < h; ++i) {
for (int j = 0; j < w; ++j) {
m.get(i).get(j).v -= d.get(i).get(j).v;
}
}
}
for (int i = 0; i < h; ++i) {
for (int j = 0; j < w; ++j) {
int k = 0;
if (i != 0) k++;
if (j != 0) k++;
if (i < h - 1) k++;
if (j < w - 1) k++;
cur[m.get(i).get(j).fixed + 1] += d.get(i).get(j).v * k;
}
}
return (cur[2] - cur[0]) / 2.0;
}
public static void main(String[] args) {
List<List<Node>> mesh = new ArrayList<>(S);
for (int i = 0; i < S; ++i) {
List<Node> t = new ArrayList<>(S);
for (int j = 0; j < S; ++j) {
t.add(new Node(0.0, 0));
}
mesh.add(t);
}
double r = 2.0 / iter(mesh, S, S);
System.out.printf("R = %.15f", r);
}
}</lang>
{{out}}
<pre>R = 1.608991241729889</pre>
=={{header|Julia}}==
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