I am getting segmentation fault for this code?

Question

i have an 2d vector of m*3 size, of which first col : lower range, second col:upper range,third col:value.and i have and initial 1-D array of size n(m

void build_tree(long long int *tree,long long int index,long long int s,long long int e)
{
    if(s==e)
    {
        tree[index]=0;
        return;
    }
    if(s>e)
        return;
    long long int mid=(s+e)/2;
    build_tree(tree,2*index,s,mid);
    build_tree(tree,2*index+1,s,mid);

    tree[index]=max(tree[2*index],tree[2*index+1]);
    return;
}
void update_range(long long int *tree,long long int index,long long int s,long long int e,long long int lower,long long int upper,int v)
{
  if(s>upper || e<lower)
  {
      return;
  }
  if(s==e && s>=lower && e<=upper)
  {
      tree[index]=tree[index]+v;
      return;
  }
  if(s>=e)
    return;

 long long int mid=(s+e)/2;
 update_range(tree,2*index,s,mid,lower,upper,v);
 update_range(tree,2*index+1,mid+1,e,lower,upper,v);

 tree[index]=max(tree[2*index],tree[2*index+1]);
 return;

}
long arrayManipulation(int n, vector<vector<int>> queries) {

 /*int a[10000000];
   // vector<int>a;
    for(int i=0;i<n;i++)
        a[i]=0;*/
    long long int *tree=new long long int(4*n+1);
    build_tree(tree,1,0,n-1);

    for(int i=0;i<queries.size();i++)
    {
        update_range(tree,1,0,n-1,queries[i][0]-1,queries[i][1]-1,queries[i][2]);
    }
    return tree[1];
}

for input n=10000000 and m=100000 i am getting segmentation fault, i have tried long long int instead of int ,but its still giving me segmentation fault.

expected output is long.

And when you ran your program in a debugger, what was the reason for the segmentation fault, that you were able to determine with your debugger? Do you know how to use a debugger? Knowing how to effectively use a debugger is a required skill for every C++ developer. If you don't know how to use a debugger, now is an excellent opportunity for you to learn this, so that you will then be able to figure out bugs in your own code, all by yourself. — Sam Varshavchik, Aug 03 '19 at 11:55

score 1 · Answer 1 · answered Aug 03 '19 at 22:51

You didn't show an MCVE, you should.

Without one, it's hard to tell exactly what is going on, but I suspect that the problem comes from this (currently commented out) code:

int a[10000000];

How big is this array? On a typical system, it's 40,000,000 bytes long. On a typical Linux system, the stack is limited to 8MiB, which is smaller than the size of the array, resulting in stack overflow. Your question is therefore duplicate of this one.

I am getting segmentation fault for this code?

1 Answers1