add numerical recipes library

lib/nr/cpp/recipes/piksr2.cpp

@@ -0,0 +1,21 @@
+#include "nr.h"
+
+void NR::piksr2(Vec_IO_DP &arr, Vec_IO_DP &brr)
+{
+	int i,j;
+	DP a,b;
+
+	int n=arr.size();
+	for (j=1;j<n;j++) {
+		a=arr[j];
+		b=brr[j];
+		i=j;
+		while (i > 0 && arr[i-1] > a) {
+			arr[i]=arr[i-1];
+			brr[i]=brr[i-1];
+			i--;
+		}
+		arr[i]=a;
+		brr[i]=b;
+	}
+}