restructure and add ipi texs

ws2019/ipi/uebungen/cpp_headers/Binsearch.cc

@@ -0,0 +1,16 @@
+template <class C>
+int binsearch (C& a, typename C::value_type x)
+{   // returns either index (if found) or -1
+  int l = 0;
+  int r = a.size();
+  while (1) {
+    int m = (l+r)/2;
+    if (m==l)
+      return (a[m]==x) ? m : -1;
+    if (x<a[m])
+      r = m;
+    else
+      l = m;
+  }
+}
+