This cpp code is not terminating. I have tried the code by various inputs but this is not terminating.I think there is a bug in the 52th line, when I comment the 52 line than the code is working fine.
#include<cstdio>
#include<iostream>
#include<vector>
#include<algorithm>
// binary search for larger elements
using namespace std;
vector <int > q;
// bsearch value uses hte
#define bvector q // just define these values to use them in your functin
#define VALUE(x) bvector[x]
int b_search(int value){
int low=0,high=bvector.size(),mid;
mid=(low+high)/2;
cout << "In the bsearch";
while(low<high)
{
if(VALUE(mid)==value)
return mid;
else if(VALUE(mid)>value)//
high=mid;
else if(VALUE(mid)<value)
low=mid+1;
}
if(VALUE(low)>value)
return low;
return -1;
}
int main(){
int i;
for(scanf("%d",&i);i;scanf("%d",&i))
q.push_back(i); // this is for taking input in the vectot
sort(q.begin(),q.end());
for(i=0;i<q.size();i++)
printf("%d ",q[i]);// for printing the sorted
int j;
printf("Enter the elements you want to search");
int x;
scanf("%d",&x);
// BUG is present in this lines
cout <<"This is the end of scanf";// if this line is commented then the 54th line is not reached
j=b_search(x);
printf("%d ",j);
return 0;
}
The statement : mid=(low+high)/2; is a bit misplaced. It should be inside the while loop.
This is probably what is causing an infinite loop.
Related
So basically,I am doing a code which searches for an element of a vector inside a vector.While I thought of the approach , implementing it got me a segmentation error. I narrowed down the problem
In the code if I decomment the line in the for loop while commenting the above then all elements of B[i] are being displayed.Why then is a segmentation error being thrown. I think the binary_return is more or less correct and if I replace the line with
binary_return(A,0,A.size(),B[1])
then its working.
Here is the code:
#include<iostream>
#include<vector>
using namespace std;
int binary_return(vector<int> a,int start,int end,int seek)
{
int mid = (start+end)/2;
//cout<<start<<" "<<seek<<" "<<mid;
if(end!=start)
{
if(a[mid]==seek)
{
return mid;
}
else if(a[mid]>seek)
{
return binary_return(a,start,mid,seek);
}
else if(a[mid]<seek)
{
return binary_return(a,mid,end,seek);
}
}
else
return -1;
}
int main()
{
vector<int> A{1,3,6,9,23};
vector<int> B{1,4,23};
cout<<B[0]<<B[1]<<B[2];
for(int i=0;i<B.size();i++)
{
cout<<binary_return(A,0,A.size(),B[i]);
//cout<<binary_return(A,0,A.size(),B[0]);
}
return 1;
}
Your code is not handling the last case correctly and ends up in infinite recursion.
This unfortunately in C++ means that anything can happen (you're not guaranteed to get a meaningful error).
Add a debug print at the beginning of the function and you'll see in which cases you're entering infinite recursion.
You have infinite recursion in third if statment
The correct code if the following:
#include<iostream>
#include<vector>
using namespace std;
int binary_return(vector<int> a,int start,int end,int seek)
{
int mid = (start+end)/2;
//cout<<start<<" "<<seek<<" "<<mid;
if(end!=start)
{
if(a[mid]==seek)
{
return mid;
}
else if(a[mid]>seek)
{
return binary_return(a,start,mid,seek);
}
else if(a[mid]<seek)
{
// In your sample you forgot to add +1 (mid+1) for next start
return binary_return(a,mid+1,end,seek);
}
}
else
return -1;
}
int main()
{
vector<int> A{1,3,6,9,23};
vector<int> B{1,4,23};
for(int i=0;i<B.size();i++)
{
cout<<binary_return(A,0,A.size(),B[i]);
}
return 0;
}
Description
This code is intended to find a spanner index (i) when dealing with
Splines/NURBS basis functions based on a knot vector (U), a choosen knot (u), the degree of the desired curve (p) and the number of basis funcions (n). The algorithm was taken from the NURBS Book by Piegl and Tiller. The error, I guess, is in the way I declared variable U. Thaks in advanced!
code
# include <iostream>
using namespace std;
int n=3;
int p=2;
double u=5/2;
int U[11]={0,0,0,1,2,3,4,4,5,5,5};
int FindSpan(n,p,u,U) /* an error in this line */
{
if (u==U[n+1]) return (n);
low=p; high=n+1;
mid=(low+high)/2
while(u<U[mid] || u>=U[mid+1])
{
if (u<U[mid]) high=mid;
else low=mid;
mid=(low+high)/2
}
return (mid);
}
You have forgotten some semicolons and types!
here is the correct code:
#include <iostream>
using namespace std;
int n=3;
int p=2;
double u=5/2;
int U[11]={0,0,0,1,2,3,4,4,5,5,5};
int FindSpan(int n, int p, int u, int U[])
{
if (u==U[n+1]) return (n);
int low=p, high=n+1;
int mid=(low+high)/2;
while(u<U[mid] || u>=U[mid+1])
{
if (u<U[mid]) high=mid;
else low=mid;
mid=(low+high)/2;
}
return (mid);
}
int main() {
cout << FindSpan(n, p, u, U);
return 0;
}
I'm having problem with this code:
#include<iostream>
#include<vector>
#include<algorithm>
#include<math.h>
using namespace std;
long long addV(int i) {
return pow(10,i);
}
int len;
void recurse(int n,long long &ways,int values[],int current=0,int p=0) {
if(p>len) return;
if(current>n) return;
if(current ==n) {
ways++;
return;
}
int cv = n-current;
cv/=values[p];
for(int i=0;i<=cv;i++) {
recurse(n,ways,values,current+values[p]*i,p+1);
}
}
int main() {
int n;
cin>>n;
long long ways=0;
int values[] ={1,2,3};
len = sizeof(values)/sizeof(int);
recurse(n,ways,values);
cout<<ways;
}
The exception comes from (cv/=values[p];) line. Of course the shitty CodeBlocks never shows what the exception is.
I'm sure its something easy to fix.
if(p>len)return;
Indeed you've already accessed over boundary when p == len. You need to return once p >= len.
Because among your ending condition for the recursion is p > len which means that p will be in the range from zero to three (inclusive). And as you know, an array of three entries have the indexes range from zero to two.
I was coding and the following code doesn't give the desired output. pos&1 is supposed to return the remainder when pos is divided by 2. When I replace pos&1 by pos%2 everything works just fine. What could be the problem?
#include <iostream>
using namespace std;
int main(){
int y;
unsigned long long int pos;
cin>>y;
cin>>pos;
int f=0;
while(y>0){
y--;
if(pos&1==0){
f=1-f;
}
pos=pos/2;
}
if(f==1){
cout<<"blue\n";
}
else
cout<<"red\n";
return 0;
}
1==0 takes more precedence than pos&1. Try if((pos&1)==0){
While I am trying to compile the code with few modification in binary search recursive function. The program is acting weird. Some time it gives the correct value and some time it goes to infinite loop. Please explain what went wrong with the code. I am using DEV C++ as an IDE.
CODE:
#include<iostream>
#include<sstream>
using namespace std;
//function to compare the two integers
int compare(int low, int high)
{
if (low==high)
return 0;
if (low<high)
return 1;
else
return -1;
}
//Function for binary search using recursion
int *BinarySearch(int *Arr,int Val,int start,int end)
{
int localstart=start;
int localend=end;
int mid=(start+end)/3;
cout<<"MID:"<<mid;
int comp= compare(Val,Arr[mid]);
if(comp==0)
return &(Arr[mid]);
else if (comp>0)
return BinarySearch(Arr,Val,localstart,mid-1);
else
return BinarySearch(Arr,Val,mid+1,localend);
return NULL;
}
main()
{
int *arr;
arr= new int [256];
string str;
getline(cin,str);
stringstream ss;
ss<<str;
int index=0;
while(ss>>arr[index])
{index++;}
//cout<<arr[index-1];
cout<<"Enter Value:";
int value;
cin>>value;
int *final;
final=BinarySearch(arr,value,0,index-1);
if(final!=NULL)
cout<<"Final:"<<*final;
else
cout<<"Not Found";
getchar();
getchar();
return 0;
}
Two ideas:
What should BinarySearch do if Val is not in the array? Trace out what your code does in this case.
(start+end)/3 probably isn't the middle of the current range.