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| import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
class Solution {
public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
int nvars = 0;
Map<String, Integer> variables = new HashMap<>();
int n = equations.size();
for (List<String> equation : equations) {
if (!variables.containsKey(equation.get(0))) {
variables.put(equation.get(0), nvars++);
}
if (!variables.containsKey(equation.get(1))) {
variables.put(equation.get(1), nvars++);
}
}
int[] f = new int[nvars];
double[] w = new double[nvars];
Arrays.fill(w, 1.0);
for (int i = 0; i < nvars; i++) {
f[i] = i;
}
for (int i = 0; i < n; i++) {
int va = variables.get(equations.get(i).get(0)), vb = variables.get(equations.get(i).get(1));
merge(f, w, va, vb, values[i]);
}
int queriesCount = queries.size();
double[] ret = new double[queriesCount];
for (int i = 0; i < queriesCount; i++) {
List<String> query = queries.get(i);
double result = -1.0;
if (variables.containsKey(query.get(0)) && variables.containsKey(query.get(1))) {
int ia = variables.get(query.get(0)), ib = variables.get(query.get(1));
int fa = find(f, w, ia), fb = find(f, w, ib);
if (fa == fb) {
result = w[ia] / w[ib];
}
}
ret[i] = result;
}
return ret;
}
public void merge(int[] f, double[] w, int x, int y, double val) {
int fx = find(f, w, x);
int fy = find(f, w, y);
f[fx] = fy;
w[fx] = val * w[y] / w[x];
}
public int find(int[] f, double[] w, int x) {
if (f[x] != x) {
int father = find(f, w, f[x]);
w[x] = w[x] * w[f[x]];
f[x] = father;
}
return f[x];
}
}
|