Program to print a histogram of the lengths of words in its input

I am supposed to write a program to print a histogram of the lengths of words in its input. When I compile my current code I get some random output... Any ideas how to solve this problem?

Ok guys… I tried to take into account your suggestions, so here is what I came up with so far:

#include <stdio.h>

int main()

{

int c, i, j, word, inspace, length;
length = 0;
word = 0;
inspace = 0;
int lengths [20];

  for (i=0; i<20; ++i)
  lengths[i] = 0;            // initialize elements
  i = 0;


   while ((c = getchar()) != EOF ) {

      if (c != ' ' && c != '\t' && c != '\n') {

      ++length;
      inspace = 1;
      if (length < 100)
      {
      ++lengths[length];
      }

      }

      if (c == ' ' || c == '\t' || c == '\n')

      {  
        if (inspace == 1) 

        inspace = 0;
        ;  
        ++word;

       }

   }

   printf( "histogram:");
  for (i=0; i<20; ++i)     {
 printf( "%2d", i);
 for (j = 0; j < lengths[i]; ++j)
    printf("*");
    printf("\n");

   }
}

Still I am getting this kind of output:

here we gohistogram: 0 1* 2* 3* 4* 5* 6* 7* 8* 9 10 11 12 13 14 15 16 17 18 19