Error message in removing duplicate strings

Hi,

My program removes the duplicate string(s) and outputs the unique strings but as soon as it does I get an error message saying stack around the variable buffer was corrupted?

Code:

---

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


int main(void)
{
      char buffer[4][4]={"cat","mat","cat","hat"};
      int i, j, k;
      int a=4;
 
      for (i = 0;i < a; i++)
      {
          for (j = i + 1; j < 4;)
          {
                if (strcmp(buffer[j],buffer[i])==0)
                {
                    for (k = j; k < a; k++)
                    {
                    strcpy(buffer[k],buffer[k+1]);
                    }

              a--;
              }

        else
        j++;
        }
    }
 
  for (i = 0; i < a; i++)
  {
      printf("%s", buffer[i]);
  }
 
  return (0);
}

---

When k = 3; then k+1 is 4 which will be undefined access.

Quote:

---

strcpy(buffer[k],buffer[k+1]);

---

Tim S.

I advise you to use an assignment of NULL as an indication that the string is removed.

I advise you to check previous strings for uniqness, not next.

I advise you to create array of pointers, not two-dimensional array of chars.

I advise you to use puts instead of printf (in such simple cases, of course).

Code:

---

const char* buffer[4] = {
  "cat",
  "mat",
  "cat",
  "hat"
};

// skipped

for( i = 0; i < 4; ++i ) {
    if( buffer[i] ) { puts(buffer[i]); }
}

---