Mergesort algorithm implementation

[nitishkj]

Below is the code which I have written to implement the mergesort algorithm in C++. It is giving segmentation fault and is stopping at line 19 (according to GDB). Please tell me my mistake/s

#include<iostream>

using namespace std;

void Merge(int* ans,int* a,int* b,int m,int n) {

  int i=0,j=0,k=0;

  while(i<=m && j<=n) {
    if(i==m) {
      ans[k] = b[j];
      k++;j++;
    }
    else if(j==n) {
      ans[k] = a[i];
      k++;i++;
    }
    else if(a[i] > b[j]) {
      ans[k] = b[j];
      k++;j++;
    }
    else {
      ans[k] = a[i];
      k++;i++;
    }
  }
}

int* MergeSort(int* a,int n) {

  if(n==1) {
    return a;
  }
  else {
    int b[n/2-1],c[n-n/2-1],i;
    int *d=0,*e=0,*ans=0;

    for(i=0;i<n/2;i++) {
      b[i] = a[i];
      c[i] = a[n/2+i];
    }
    if(n%2 == 1) {
	c[i] = a[n-1];
    }
    d = MergeSort(b,n/2);
    e = MergeSort(c,n-n/2);
    Merge(ans,d,e,n/2,n-n/2);
    return ans;
  }
}

int main() {

  int a[] = {9,8,7,6,5,4,3,2,1},i;
  int *b=0;
  b = MergeSort(a,9);

  for(i=0;i<9;i++)
    cout<<b[i]<<endl;
}

It is giving the following message in GDB

Program received signal SIGSEGV, Segmentation fault.
0x0000000000400a29 in Merge (ans=0x0, a=0x7fffffffde50, b=0x7fffffffde40, m=1, n=1) at mergesort.cpp:19
19 ans[k] = b[j];