add numerical recipes library

lib/nr/cpp/recipes/eclass.cpp

@@ -0,0 +1,19 @@
+#include "nr.h"
+
+void NR::eclass(Vec_O_INT &nf, Vec_I_INT &lista, Vec_I_INT &listb)
+{
+	int l,k,j;
+
+	int n=nf.size();
+	int m=lista.size();
+	for (k=0;k<n;k++) nf[k]=k;
+	for (l=0;l<m;l++) {
+		j=lista[l];
+		while (nf[j] != j) j=nf[j];
+		k=listb[l];
+		while (nf[k] != k) k=nf[k];
+		if (j != k) nf[j]=k;
+	}
+	for (j=0;j<n;j++)
+		while (nf[j] != nf[nf[j]]) nf[j]=nf[nf[j]];
+}