CODEWITHSUNDEEP
c++c
user3508140
user3508140

Reputation: 285

Runtime error when I run the program but not when i use debugger

I'm trying to make a c/c++ program where the program accepts a txt file with several words, one per line, and finds the edit distance(also called levenshtein distance) with a specific word.

I have a weird problem.

My code encounters a runtime error after a reading a couple of words when I run it in code-blocks. It debugs fine when i use the code-blocks debugger.

I have been looking around and I found uninitialised variables can be a problem. But whenever i comment the line where i am calling the function minDistance count[i]=minDistance(word,lines[i]);, the code runs fine and prints out all the words in the file. So that's not a problem I guess.

Any help would be great. Thank you.

Following is the code.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include<iostream>


using namespace std;
static int minDistance(char* word1, char* word2)
{
    const int l1 = strlen(word1);
    const int l2 = strlen(word2);
    int i=0,j=0;
    int **d = new int*[l2 + 1];
    for(i=0;i<l1+1;++i)
        d[i]=new int[l1+1];

    // the edit distance between an empty string and the prefixes of
    // word2
    for (i = 0; i < l2 + 1; i++) {
        d[0][i] = i;
    }

    // the edit distance between an empty string and the prefixes of
    // word1
    for (j = 0; j < l1 + 1; j++) {
        d[j][0] = j;
    }

    for (i = 1; i < l1 + 1; i++) {
        for (j = 1; j < l2 + 1; j++) {
            if (word1[i - 1] == word2[j - 1]) {
                d[i][j] = d[i - 1][j - 1];
            } else {
                d[i][j] = min(min(1 + d[i][j - 1], 1 + d[i - 1][j]),
                1 + d[i - 1][j - 1]); // min of insertion,
                // deletion, replacement
            }
        }
    }

    return d[l1][l2];
}

void lines()
{
  int i=0;
  char * lines[10];
  int count[10];
  char word[]="book";
  FILE *file_handle = fopen ("wordlist.txt", "r");

  for (i =0; i < 5; ++i)
    {
    lines[i] = (char*)malloc (128); /* allocating a memory slot of 128 chars */
    fscanf (file_handle, "%s", lines[i]);
    count[i]=minDistance(word,lines[i]);
    cout<<lines[i]<<" ";
    cout<<count[i]<<endl;
    }

  for (i =0; i < 5; ++i)
    free (lines[i]);

}
int main (int argc, char *argv[])
{
  lines();
  return 0;
}

Upvotes: 1

Views: 87

Answers (2)

sandman
sandman

Reputation: 119

You use l2 as your second index. It should be your first index and l1 your second index.

// the edit distance between an empty string and the prefixes of
// word2
for (i = 0; i < l1 + 1; i++) {
    d[0][i] = i;
}

Upvotes: 0

a_pradhan
a_pradhan

Reputation: 3295

Notice the lines in your code :

int **d = new int*[l2 + 1];
for(i=0;i<l1+1;++i)

You are allocating memory for (l2 + 1) number of int* and you are looping i from 0 to (l1 + 1). So if l2 < l1, you are accessing memory you have not allocated.

Also don't mix C++ and C. Either use C or stick with C++. As mentioned in the comments, if you can use C++, use std::vector and std::string - it will reduce your headache. Also use C++'s IO classes to perform File IO and always close any file you have opened. (i.e. in C, use fclose(file_ptr) ).

Upvotes: 2

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