add numerical recipes library

lib/nr/cpp/recipes/hpsel.cpp

@@ -0,0 +1,25 @@
+#include "nr.h"
+
+void NR::hpsel(Vec_I_DP &arr, Vec_O_DP &heap)
+{
+	int i,j,k;
+
+	int m=heap.size();
+	int n=arr.size();
+	if (m > n/2 || m < 1) nrerror("probable misuse of hpsel");
+	for (i=0;i<m;i++) heap[i]=arr[i];
+	sort(heap);
+	for (i=m;i<n;i++) {
+		if (arr[i] > heap[0]) {
+			heap[0]=arr[i];
+			for (j=0;;) {
+				k=(j << 1)+1;
+				if (k > m-1) break;
+				if (k != (m-1) && heap[k] > heap[k+1]) k++;
+				if (heap[j] <= heap[k]) break;
+				SWAP(heap[k],heap[j]);
+				j=k;
+			}
+		}
+	}
+}