solutions

exams/p2014-11-20/area.cc

@@ -6,19 +6,21 @@
 
 double area(double* x,double* y,unsigned n)
 {
- double s=0; //sum
+ double a=0;
  for(unsigned i=1;i<n;++i)
  {
-  s=s+(x[i-1]*y[i]-y[i-1]*x[i]);
+  a+=(x[i-1]*y[i] -  y[i-1]*x[i]);
  }
- s=s+(x[n-1]*y[0]-y[n-1]*x[0]);
- return 0.5*s;
+ a+=(x[n-1]*y[0]-y[n-1]*x[0]);
+ return 0.5*a;
 }
 
+
 int main(int argc,char** args)
 {
- double x[]={ -0.0400682349440255,  0.8609006329573937,  0.4270168938398355, -0.4739519740615837};
- double y[]={  0.3136790342824826,  0.7475627734100397,  1.6485316413024589,  1.2146479021849006};
- std::cout<<"a="<<area(x,y,4)<<"\n";
+ double x[]={1,2,2,1};
+ double y[]={5,5,6,6};
+ double a=area(x,y,4);
+ std::cout<<"a="<<a<<"\n";
  return 0;
 }

exams/p2014-11-20/exp2.cc

+//----------------------
+//exp2
+//(c) H.Buchmann FHNW 2014
+//----------------------
+#include <iostream>
+#include <sstream>
+bool isExp2(unsigned val)
+{
+ return (val&(-val))==val;
+}
+
+unsigned toUnsigned(char* s)
+{
+ std::stringstream ss(s);
+ unsigned v=0;
+ ss>>v;
+ return v;
+}
+
+int main(int argc,char** args)
+{
+ unsigned v=toUnsigned(args[1]);
+    
+ std::cerr<<"isExp2("<<v<<")="<<isExp2(v)<<"\n";
+}
+

exams/p2014-11-20/ld2.cc

@@ -5,9 +5,18 @@
 #include <iostream>
 #include <iomanip>
 
- ld2(unsigned val)
+unsigned ld2(unsigned val)
 {
  static const unsigned N=sizeof(val)*8; //the number of bits 
+ unsigned log=N;
+ unsigned m=(1<<(N-1));
+ while(m)
+ {
+  --log;
+  if (val&m) return log;
+  m>>=1;
+ }
+ return log-1;
 }
 
 

exams/p2014-11-20/unsigned.cc

@@ -54,25 +54,6 @@ unsigned String::hexDigit(char ch)
  return 10+(ch-'a');
 }
 
-/* the fragments
-
-
-(--------------------------------------A 
---------------------------------------A )
-
-(-------------------------------------- B
--------------------------------------- B)
- 
-(-------------------------------------- C
--------------------------------------- C)
-
-
-(-------------------------------------- D
--------------------------------------- D)
-
-(-------------------------------------- E
--------------------------------------- E)
-*/
 bool String::to(char* s,unsigned* val)
 {
  unsigned i=0; //index in s
@@ -83,49 +64,49 @@ bool String::to(char* s,unsigned* val)
   char ch=s[i++];
   switch(status)
   {
-   case 0: 
+   case 0:
     if (ch=='0')
        {
         v=0;
-        status=2;
+        status=1;
 	break;
        }
     if (isDecDigit(ch))
        {
         v=decDigit(ch);
-	status=1;
+	status=2;
 	break;
        }
    return false;
   
    case 1: 
-    if (ch=='\0')
+    if (ch=='\0') 
        {
         *val=v;
 	return true;
        }
+    if ((ch=='x')||(ch=='X'))
+       {
+        status=3;
+	break;
+       }
     if (isDecDigit(ch))
        {
         v=10*v+decDigit(ch);
+	status=2;
 	break;
        }
    return false;
    
    case 2:
-    if (ch=='\0') 
+    if (ch=='\0')
        {
         *val=v;
 	return true;
        }
-    if ((ch=='x')||(ch=='X'))
-       {
-        status=3;
-	break;
-       }
     if (isDecDigit(ch))
        {
         v=10*v+decDigit(ch);
-	status=1;
 	break;
        }
    return false;

exams/p2014-11-20/utf8-string.cc

@@ -13,38 +13,35 @@ class UTF8String
 //assuming correct utf-8 string
 unsigned UTF8String::len(char* s)
 {
+ unsigned l=0; //the char count
  unsigned i=0; //index in s
- unsigned l=0; //length l<=i
  while(true)
  {
-  char ch=s[i];
-  if (ch=='\0') break;
-  l++;
-  if ((ch&0b10000000)==0)
+  char ch=s[i]; //current char
+  if (ch=='\0') return l;
+  if ((ch&(1<<7))==0)
      {
-      i++;
-      continue; // next step in while loop
+      ++i;
+      ++l;
+      continue;
      }
-  //0x11xx xxxx
-  if ((ch&0b00100000)==0)
+// 0x11z x xxxx
+  if ((ch&(1<<5))==0)
      {
       i+=2;
+      ++l;
       continue;
      }
-  //0x111x xxxx 
-  if ((ch&0b00010000)==0)
+// 0x111z xxxx
+  if ((ch&(1<<4))==0)
      {
       i+=3;
+      ++l;
       continue;
      }
-  //0x1111 xxxx 
-  if ((ch&0b00001000)==0)
-     {
-      i+=4;
-      continue;
-     }
- }
- return l;
+  i+=4;
+  ++l;  
+ }  
 }
 
 int main(int argc,char** args)