runtime error(SIGSEGV) for lowest sum

    #include<stdio.h>
#include<stdlib.h>
void quicksort(int*,int,int);
int partition(int*,int,int);
void swap(int*,int*,int*);

int main()
{
 int t,k,q,i,j,p,*a,*b,*sum,qi,c;
 //printf("Enter no of test cases");
 scanf("%d",&t);
 for(i=0;i<t;i++)
 {
  p=0;
  //printf("Enter no of chefs and no of queries");
  scanf("\n%d %d",&k,&q);
  a=(int*)malloc(k*sizeof(int));
  b=(int*)malloc(k*sizeof(int));
  sum=(int*)malloc(k*k*sizeof(int));
  //printf("Enter satisfaction levels");
  for(j=0;j<k;j++)
  scanf("%d",&a[j]);
  //printf("Enter motivation levels");
  for(j=0;j<k;j++)
  scanf("%d",&b[j]);
  //calc sum[]
  for(c=0;c<k;c++)
  for(j=0;j<k;j++)
  sum[p++]=a[c]+b[j];
  free(a);
  free(b);
  quicksort(sum,0,--p);       //partition,swap
  for(j=0;j<q;j++)
  {
   //printf("\n qith lowest sum");
   scanf("\n%d",&qi);
   printf("%d",sum[qi-1]);
  }
  free(sum);
 }
 return 0;
}

void quicksort(int sum[],int low,int high)
{
 int m;
 if(low<high)
 {
  m=partition(sum,low,high);
  quicksort(sum,low,m-1);
  quicksort(sum,m+1,high);
  }
}

int partition(int sum[],int low,int high)
{
 int pivot=sum[low],i=low,j=high;
 while(i<=j)
 {
  while(sum[i]<=pivot)
  i++;
  while(sum[j]>pivot)
  j--;
  if(i<j)
  swap(sum,&i,&j);
  }
  swap(sum,&low,&j);
  return j;
}

void swap(int sum[],int *i,int *j)
{
 int temp;
 temp=sum[*i];
 sum[*i]=sum[*j];
 sum[*j]=temp;
}

getting a runtime error(SIGSEGV) neither i am accessing an array which is out of bounds nor i am using a variable which i haven't initialised Also my main function returns 0. Not getting whats the cause of the error ?