binary search

cia

5-pointer/src/binary-search-generic.cc

+//-----------------------
+//binary-search
+//(c) H.Buchmann FHNW 2011
+//-----------------------
+#include <iostream>
+
+/*
+ data ordered i<j -> data[i]<=data[j]
+
+ returns index
+  0<=index<len
+  if val in data then data[index]==val
+*/
+
+/*
+data   |---|---|---|---|---|---|---|---|---|... 
+index    0   1   2   3   4   5   6   7   8   |
+len                                          9
+
+before 
+beg<end
+end-beg: number of elements
+                         m
+         0   1   2   3   |   5   6   7   8   9
+data   |---|---|---|---|---|---|---|---|---|...
+index    |                                   |
+         beg                                 end
+m=floor((beg+end)/2) 
+beg<=m<end
+
+if val<data[m]
+                                 m
+                                 |
+	data   |---|---|---|---|...|...|...|...|...|...
+        	 |               |
+		 beg             end
+
+if (val>=data[m])
+       	data   |...|...|...|...|---|---|---|---|---|...
+	                         |                   |
+				 beg                 end	
+*/ 
+
+/*
+ 1. recursive
+ 2. while loop
+*/
+
+
+template<typename T>
+const T* binary_search(T val,const T* beg,const T* end)
+{
+ while((end-beg)>1)
+ {
+  auto m=beg+(end-beg)/2;
+  if (val<*m)
+     {
+      end=m;
+     }
+     else
+     {
+      beg=m;
+     }
+ }
+ return beg;
+}
+
+template<typename T>
+void singleTest(T val,const T* beg,const T* end)
+{
+ std::cout<<"start--------\n";
+ auto res=binary_search(val,beg,end);
+ std::cout<<"res="<<res<<"\n";
+}
+
+template<typename T>
+void selfTest(const T* beg,const T* end)
+{
+ for(auto v=beg;v!=end;++v)
+ {
+  auto loc=binary_search(*v,beg,end); 
+  if (*v!=*loc)
+     {
+      std::cout<<"error\n";
+      return;
+     }
+ }
+ std::cout<<"ok\n";
+}
+
+
+void setData(int d[],unsigned len)
+{
+ int v=0;
+ for(unsigned i=0;i<len;++i)
+ {
+  d[i]=v;
+  v+=2;
+ }
+}
+
+static const unsigned LEN=(1<<4);
+int data[LEN];
+
+int main(int argc,char* args[])
+{
+//crash if data on stack
+ setData(data,LEN);
+// singleTest(100'000'000,data,LEN);
+ selfTest(data,data+LEN);
+ return 0;
+}

5-pointer/src/binary-search.cc

@@ -47,7 +47,16 @@ if (val>=data[m])
 */
 
 
+
+/* return:
+    index: 0<=<index<len
+   test if val in data
+   data[index]==val    
+*/
+unsigned binarySearch(int val,int data[],unsigned len)
+{
 /* your work */
+}
 
 void singleTest(int val,
                 int data[],unsigned len)

5-pointer/src/main-args.cc

@@ -6,9 +6,9 @@
 #include <iostream>
 
 //Java void main(String args[])
-//int main(int argc,char*args[]) alternative
+//int main(int argc,char* args[]) alternative
 int main(int argc,char** args)
-       //|                  |----- array of pointer (char*)
+       //|                  |----- array of pointer (char*) array of strings
        //|                    array of strings 
        //+------------------- length of array 
 {

5-pointer/src/string-demo.cc

@@ -17,7 +17,7 @@ int main(int argc,char* args[])
  s[7]='e';
  s[8]='l';
  s[9]='t';  //not a proper end of string no terminating zero 
-// s[10='\0'; //<--out of range
+// s[10]='\0'; //<--out of range
 // char* sP=s;
  std::cout<<"s= "<<s<<"\n";
  return 0;

5-pointer/src/string.cc

@@ -77,6 +77,13 @@ int String::isHexDigit(char ch)
 //implementation
 unsigned String::len(char* s)
 {
+ if (s==0) return 0;
+ unsigned i=0; //index in s
+ while(s[i]!='\0)
+ {
+  i=i+1; //++i i++
+ }
+ return i;
 }
 
 

ziele-vz.md

@@ -75,4 +75,9 @@
          - ``string.cc`` exercises.pdf Aufgaben 5.1, 5.2, 5.4, 5.8, 5.9
             
    
-      
+## 12.11.2020
+ - 5-pointer
+     - Strings ``string.cc`` exercises.pdf Aufgaben 5.2, 5.4, 5.8, 5.9
+ - 6-cia 
+      - Die Klasse ``Point`` Folien Seite 7
+      - exercises.pdf Aufgaben 1.1, 1.2, 1.3