C程序-段故障，原因

Question

Running this gives me a seg fault (gcc filename.c -lm), when i enter 6 (int) as a value. Please help me get my head around this. The intended functionality has not yet been implemented, but I need to know why I'm headed into seg faults already.

Thanks!

#include<stdio.h>
#include<math.h>
int main (void)
{
  int l = 5;
  int n, i, tmp, index;
  char * s[] = {"Sheldon", "Leonard", "Penny", "Raj", "Howard"};
  scanf("%d", &n);

  //Solve Sigma(Ai*2^(i-1)) = (n - k)/l     

  if (n/l <= 1)
    printf("%s\n", s[n-1]); 
  else
    {
      tmp = n;
      for (i = 1;;)
    {
      tmp = tmp - (l * pow(2,i-1));
      if (tmp <= 5) 
        {
          // printf("Breaking\n");
          break;
        }
      ++i;
    }
      printf("Last index = %d\n", i);   //  ***NOTE***

      //Value lies in next array, therefore
      ++i;

      index = tmp + pow(2, n-1);
      printf("%d\n", index);

    }
  return 0;
}

Answer 1

When you input 6 for n and s[n-1] , you are doing out of bounds access:

printf("%s\n", s[n-1]); 

Because there are only 5 pointers in the array. So only 0-4 are valid indexes.

Answer 2

You are using pow function, which is not so efficient.

here is my solution in Python.

from math import ceil

names = ['Sheldon', 'Leonard', 'Penny', 'Rajesh', 'Howard']

n = int(raw_input())

i = 0
j = 1
k = len(names)

while i <= n:
    i += k
    k += k
    j += j

print names[int(ceil((n - (i - k * 0.5)) / (j * 0.5)) - 1)]

I hope this helps.