This is a question from oj PAT
Insert a sequence of given numbers into an initially empty min-heap H. Then for any given index i, you are supposed to print the path from H[i] to the root.
However, my code always time out, i.e, it takes too long time. How to solve it?
main()
{
int i,*a,n,m,k,data;
scanf("%d%d",&n,&m);
a=malloc(n*sizeof(int));
a[0]=-10001; //
for(i=1;i<=n;i++)
{
scanf("%d",&data);
heapAdjust(a,data);
}
for(i=1;i<=m;i++)
{
scanf("%d",&k);
printf("%d",a[k]);
k=k/2;
while(1)
{
printf(" %d",a[k]);
if(k==1)
break;
k=k/2;
}
printf("\n");
}
free(a);
}
void heapAdjust(int a[],int data) // make heap
{
static int size=0;
int i;
i=++size;
for(;a[i/2]>data;i=i/2)
a[i]=a[i/2];
a[i]=data;
}
You are probably running into an infinite loop because k becomes zero at some point.
Try changing the break condition inside the while(1) loop from k == 1 to k <= 1 and see if that helps.
Related
I've tried to write a program that removes the duplicate values from an array. I've partly managed to do so since my program is able to remove any ONE of the numbers which are repeated TWICE in the array. So the problem is that if a number is repeated thrice only one of the number is removed, i.e. the other two is still left in the array, also if more than one number is repeated even then only the number which comes first in the array is removed. I really cannot understand what's wrong with my code and why is it unable to remove numbers that are repeated more than two times. I've already surfed through the internet regarding this issue and though I got different ways to remove the duplicate elements, I still don't know what's wrong with my code.
#include <stdio.h>
#include <stdlib.h>
int dup(int [],int);
int main()
{
int i,n,index,a[20];
printf("Enter n value \n");
scanf("%d",&n);
printf("Enter array values \n");
for(i=0;i<n;++i)
scanf("%d",&a[i]);
for(i=0;i<n;++i)
{
index=dup(a,n);
if(index==-1)
{
printf("No duplicate elements");
break;
}
else
{
a[index]=0;
for(i=index;i<n;i++)
a[i]=a[i+1];
n-=1;
}
}
printf("Output: \n");
for(i=0;i<n;++i)
printf("%d\n",a[i]);
return (EXIT_SUCCESS);
}
int dup(int a[],int size)
{
int i,j,pos=-1;
for(i=0;i<size;i++)
{
for(j=i+1;j<size;j++)
{
if(a[i]==a[j])
{
pos=j;
return pos;
}
}
}
if(pos==-1)
return pos;
}
OUTPUT
Enter n value
5
Enter array values
12
24
3
12
24
Output:
12
24
3
24
It clearly fails to remove the other repeated element "24". Also if a number was repeated thrice only one of the number would be removed.
for(i=0;i<n;++i) // <-------------------------------------- for i
{
index=dup(a,n);
if(index==-1)
{
printf("No duplicate elements");
break;
}
else
{
a[index]=0;
for(i=index;i<n;i++) // <--------------------------- for i
a[i]=a[i+1];
n-=1;
}
}
You are using the same loop variable for two loops, one nested inside the other. This cannot work. Use different variables. Live demo.
The Problem seem to lie in the if condition in second loop.
for (k = j; k < size; k++) {
arr[k] = arr[k + 1];
}
Simply put this piece of code after your if condition
if(a[i]==a[j])
and it will work.
My mistake, at first glence I thought you had problem with n after running this it worked.
#include <stdio.h>
#include <stdlib.h>
int dup(int [],int);
int main()
{
int i,n,index,a[20], count;
printf("Enter n value \n");
scanf("%d",&n);
count = n;
int j;
printf("Enter array values \n");
for(i=0;i<n;++i)
scanf("%d",&a[i]);
for(i=0;i<n;++i)
{
index=dup(a,n);
if(index==-1)
{
printf("No duplicate elements");
break;
}
else
{
a[index]=0;
for(j=index;j<n;j++)
a[j]=a[j+1];
n-=1;
}
}
printf("Output: \n");
for(i=0;i<n;++i)
printf("%d\n",a[i]);
return (EXIT_SUCCESS);
}
int dup(int a[],int size)
{
int i,j,pos=-1;
for(i=0;i<size;i++)
{
for(j=i+1;j<size;j++)
{
if(a[i]==a[j])
{
pos=j;
return pos;
}
}
}
if(pos==-1)
return pos;
}
OUTPUT
Enter n value
5
Enter array values
12
24
3
12
24
Output:
12
24
3
You should name your iterator variables better so you might not confuse them in nested loops, or as you do, use the same twice in a nested loop.
This skips all variables after your first removal.
and you don't have to do this
if(pos==-1)
return pos;
skip the if as it is not necessary and if at this position posis not -1then you would have no return which would be UB I think.
I wrote a program that should take an array of numbers and find the array index of the smallest number. However, when I type the numbers with spaces between and then press enter, the program keeps running. What can be the cause? Here is the code:
#include<stdio.h>
//read numbers to an array
//find minimum
//print the index of minimum
double findMinimum(int size,double array[]){
int n;
int minIndex=0;
for(n=1;n<size;size++){
if(array[n]<array[n-1]){
minIndex=n;
}
}
return minIndex;
}
int main(){
setvbuf(stdout,NULL,_IONBF,0);
int size=0;
double inArray[size];
printf("Enter an array of numbers:");
int k=0;
char c;
while(c!='\n'){
c=getchar();
if(c=='\n'){
break;
}
scanf("%lf",&inArray[k]);
k++;
size++;
};
int minIndex=0;
minIndex=findMinimum(size,inArray);
printf("The index of minimum number is %i",minIndex);
return 0;
}
I also took the part of the code that scans numbers to an array. I tried to change the while loop and used "break" statement, but the output gave all numbers in an array except the first one. Here is the code:
#include<stdio.h>
//read numbers to an array
int main(){
setvbuf(stdout,NULL,_IONBF,0);
int size=0;
double inArray[size];
printf("Enter an array of numbers ending with question mark:\n");
int k=0;
char c;
while(1){
c=getchar();
if(c=='?'){
break;
}
scanf("%lf",&inArray[k]);
k++;
size++;
};
int n;
for(n=0;n<size;n++){
printf("%f\n",inArray[n]);
}
return 0;
}
Thanks for help in advance!
for(n=1;n<size;size++){
if(array[n]<array[n-1]){
minIndex=n;
}
}
The issue in your code is you are incrementing size, thats why your loop is not terminating. increment n
Edit
you have initialized your 'n' with 1 , however arrays start with zero index thats why it misses the first element,
for(n=0;n<size;n++){
if(array[n]<array[minIndex]){
minIndex=n;
}
}
try this one :
for(n=1; n < size; n++){
if(array[n]<array[minIndex]){
minIndex=n;
}
}
I'm trying to implement odd-even sort program in cuda-c language. But, whenever I give a 0 as one of the elements in the input array, the resulted array is not properly sorted.In other cases, however, it is working for other input.I don't understand what is the problem with the code.Here is my code:
#include<stdio.h>
#include<cuda.h>
#define N 5
__global__ void sort(int *c,int *count)
{
int l;
if(*count%2==0)
l=*count/2;
else
l=(*count/2)+1;
for(int i=0;i<l;i++)
{
if(threadIdx.x%2==0) //even phase
{
if(c[threadIdx.x]>c[threadIdx.x+1])
{
int temp=c[threadIdx.x];
c[threadIdx.x]=c[threadIdx.x+1];
c[threadIdx.x+1]=temp;
}
__syncthreads();
}
else //odd phase
{
if(c[threadIdx.x]>c[threadIdx.x+1])
{
int temp=c[threadIdx.x];
c[threadIdx.x]=c[threadIdx.x+1];
c[threadIdx.x+1]=temp;
}
__syncthreads();
}
}//for
}
int main()
{int a[N],b[N],n;
printf("enter size of array");
scanf("%d",&n);
print("enter the elements of array");
for(int i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
printf("ORIGINAL ARRAY : \n");
for(int i=0;i<n;i++)
{
printf("%d ",a[i]);
}
int *c,*count;
cudaMalloc((void**)&c,sizeof(int)*N);
cudaMalloc((void**)&count,sizeof(int));
cudaMemcpy(c,&a,sizeof(int)*N,cudaMemcpyHostToDevice);
cudaMemcpy(count,&n,sizeof(int),cudaMemcpyHostToDevice);
sort<<< 1,n >>>(c,count);
cudaMemcpy(&b,c,sizeof(int)*N,cudaMemcpyDeviceToHost);
printf("\nSORTED ARRAY : \n");
for(int i=1;i<=n;i++)
{
printf("%d ",b[i]);
}
}
Your kernel code had two main errors that I could see:
On the odd phase (for even length array, or even phase for odd length array), your last thread will index out of bounds at c[threadIdx.x+1]. For example, for 4 threads, they are numbered 0,1,2,3. Thread 3 is odd, but if you access c[3+1], that is not a defined element in your array. We can fix this by restricting each phase to work on all threads but the last one.
You were using __syncthreads() inside a conditional statement that would not allow all threads to reach the barrier. This is a coding error. Read the documentation. We can fix this by adjusting what code is inside the conditional regions.
In the main code, your final printout statements were indexing incorrectly:
for(int i=1;i<=n;i++)
that should be:
for(int i=0;i<n;i++)
You also have typo here:
print("enter the elements of array");
I assume that should be printf.
The following code has the above errors fixed, and seems to run correctly for me for arrays up to length 5 (your hardcoded limit on N). Even if you increased N, I'm not sure this would work beyond the size of a warp and certainly would not work beyond the threadblock size, but hopefully you are aware of that already(if not, read the doc link about __syncthreads()).
"Fixed" code:
#include<stdio.h>
#include<cuda.h>
#define N 5
#define intswap(A,B) {int temp=A;A=B;B=temp;}
__global__ void sort(int *c,int *count)
{
int l;
if(*count%2==0)
l=*count/2;
else
l=(*count/2)+1;
for(int i=0;i<l;i++)
{
if((!(threadIdx.x&1)) && (threadIdx.x<(*count-1))) //even phase
{
if(c[threadIdx.x]>c[threadIdx.x+1])
intswap(c[threadIdx.x], c[threadIdx.x+1]);
}
__syncthreads();
if((threadIdx.x&1) && (threadIdx.x<(*count-1))) //odd phase
{
if(c[threadIdx.x]>c[threadIdx.x+1])
intswap(c[threadIdx.x], c[threadIdx.x+1]);
}
__syncthreads();
}//for
}
int main()
{int a[N],b[N],n;
printf("enter size of array");
scanf("%d",&n);
if (n > N) {printf("too large!\n"); return 1;}
printf("enter the elements of array");
for(int i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
printf("ORIGINAL ARRAY : \n");
for(int i=0;i<n;i++)
{
printf("%d ",a[i]);
}
int *c,*count;
cudaMalloc((void**)&c,sizeof(int)*N);
cudaMalloc((void**)&count,sizeof(int));
cudaMemcpy(c,&a,sizeof(int)*N,cudaMemcpyHostToDevice);
cudaMemcpy(count,&n,sizeof(int),cudaMemcpyHostToDevice);
sort<<< 1,n >>>(c,count);
cudaMemcpy(&b,c,sizeof(int)*N,cudaMemcpyDeviceToHost);
printf("\nSORTED ARRAY : \n");
for(int i=0;i<n;i++)
{
printf("%d ",b[i]);
}
printf("\n");
}
The usual recital about proper cuda error checking belongs here.
I wrote this program which takes n and k as input and then takes an array a[n] as input. The program must give the output as the total no of distinct integers in array a that are less than k and odd. But this program with every input is producing 0 as output.
#include<stdio.h>
int main()
{
long long int n,i,j,k,temp=-1;
scanf("%lld %lld",&n,&k);
long long int a[n];
for(i=0;i<n;i++)
scanf("%d",&a[i]);
long long int cnt=0;
for(i=0;i<n;i++)
{
if(a[i]<k)
{
if((a[i]%2)==1)
cnt++;}
}
for(i=0;i<(n-1);i++)
{
for(j=i+1;j<n;j++)
{
if(a[i]==a[j])
{
cnt--;
a[j]=temp;
--temp;
}
}
}
printf("%lld",cnt);
return 0;
}
scanf("%d", &a[i]);
Must be:
scanf("%lld", &a[i]);
check out the inner for loop, maybe you need to declare a variable and increment that and write and if statement that says, if variable==1 then print the desired value.
Not sure but might work.
According to the problem we have to find whether an element occurs more than n/2 times or not and then print Yes or No accordingly.
The numbers can vary from 10^-3 to 10^3.
I took an array count[2005] and then adding 1000 to each input to make 10^-3 equal to 0 i.e, -1000+1000=0 and then storing no.of occurrences of -1000 in count[0] and same for the rest elements. Therefore:
lower limit= -1000+1000=0;
higher limit= 1000+1000=2000;
But still I am getting memory access violation. Here is the link to the original problem: http://www.spoj.com/problems/MAJOR/
#include<stdio.h>
int main()
{
int t,n,a,count[2005],max,check,temp;
scanf("%d",&t);
while(t--)
{
check=0;
scanf("%d",&n);
for(int i=0;i<2005;i++)
count[i]=0;
for(int i=0;i<n;i++)
{
scanf("%d",&a);
temp=a+1000;
count[temp]++;
if(count[temp]>(n/2))
{
check=1;
max=temp-1000;
break;
}
}
if(check==1)
printf("YES %d\n",max);
else
printf("NO\n");
}
return 0;
}
Problem to your code is you are not reading input fully - SPOJ demands that your program should read input fully, not break in middle.
Solution to your problem: Just take an arr of size (10^6+1) and first read all inputs and then apply algorithm. Remember this if you break while reading input too, it will always be SIGSEGV. So, always read input fully on every programming website.
Here is your modified code and it is ready to get AC:
#include<stdio.h>
int arr[1000002]; // Array of Size (10^6+2)
int main()
{
int t,n,a,count[2005],max,check,temp,i;
scanf("%d",&t);
while(t--)
{
check=0;
scanf("%d",&n);
for(int i=0;i<2005;i++)
count[i]=0;
for(i=0;i<n;i++)
scanf("%d",&arr[i]); // READING INPUT FULLY IN AN ARRAY
for(i=0;i<n;i++)
{
a=arr[i]; // Now, a=arr[i] and previous algorithm applies now
temp=a+1000;
count[temp]++;
if(count[temp]>(n/2))
{
check=1;
max=temp-1000;
break;
}
}
if(check==1)
printf("YES %d\n",max);
else
printf("NO\n");
}
return 0;
}