在C编程中基于另一个字符串数组的字删除字符串数组中的字

Question

I am trying to write a C program to delete some words from an Array of String (chars) in C programming based on another Array of String (chars).

I have written a program like the following.

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

void main()
{
    int i, j, k, flag;
char Name[200][100] = {"descent","of","man","the","ascent","of","man","the","old","man","and","the","sea","a","portrait","of","the","artist","as","a","young","man"};
char Delete[200][100] = {"the","of","and","as","a"};

printf("Words are : \n\n");
for (i = 0; i<22; i++)
{
    printf("%s, ", Name[i]);
}

printf("\n\nWords for deletion are: \n\n");

for (i = 0; i<5; i++)
{
    printf("%s, ", Delete[i]);
}

printf("\n\n");


for(i=0; i<5; i++)
{
    flag = 0;

    for(j=0; j<22; j++)
    {
        if(strcmp(Name[i],Delete[j]) == 0)
        {
            flag = 1;
        }

        if (flag == 1)
        {
            for (k = j; k<22-1; k++)
            {
                strcpy(Name[k],Name[k+1]);
            }

            strcpy(Name[22-1],"");
        }
    }
}

printf("Words after deletion is : \n\n");

for (i = 0; i<22; i++)
{
    printf("%s ", Name[i]);
}

printf("\n");
}

But unfortunately, the program is not working as desired. I am not understanding what I am doing wrong in here. Can anyone please suggest me what I am doing wrong in here or an easier way of doing it. Thanks in advance.

Answer 1

Try this. The initial lists have had an empty string added to the end as a sentinel, and the loops have been changed to use the sentinels. When the string to be deleted is detected, I change the first char to 0x1A (the ASCII control char for "substitution occurred" - chosen somewhat arbitrarily). Then I walk the word list once, and when I find a sub char, i skip that string and then 'compress out' the deleted words by copying over them from the next non-null string without a sentinel char in it. I could have used some trickery to avoid the second pass and copy things over in the main loop, but I did not want to over combine the logic for you.

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

void main()
{
   int i, j;
   /* both lists end with a sentinal string of ""  */
   char Name[200][100] = {"descent","of","man","the","ascent","of","man","the","old","man","and","the","sea","a","portrait","of" ,"the","artist","as","a","young","man",""};
   char Delete[200][100] = {"the","of","and","as","a", ""};

   printf("Words are : \n\n");
   for( i=0; Name[i][0] != 0x00; i++ ) {
      printf("%s, ", Name[i]);
   }

   printf("\n\nWords for deletion are: \n\n");
   for( j=0; Delete[j][0] != 0x00; j++ ) {
      printf("%s, ", Delete[j]);
   }
   printf("\n\n");

   /* mark for removal */
   for( i=0; Name[i][0] != 0x00; i++ ) {
      for( j=0; Delete[j][0] != 0x00; j++ ) {
         if(strcmp(Name[i],Delete[j]) == 0) {
            Name[i][0]=0x1A; /* ASCII ctrl char for substitute - chosen arbitrarily */
         }
      }
   }

   /* one pass to remove */
   for( i=0, j=0; Name[i][0] != 0x00; i++,j++ ) {
      while( Name[i][0] == 0x1A )
         i++;

      if(i!=j)
         strcpy(Name[j],Name[i]);
   }
   strcpy(Name[j],Name[i]);

   printf("Words after deletion are: \n\n");

   for( i=0; Name[i][0] != 0x00; i++ ) {
      printf("%s ", Name[i]);
   }
   printf("\n");
}

Answer 2

First off you need to keep track of the number of elements in each array

 size_t numName = 22;
 size_t numDelete = 5;

The issue is in the line for(j=0; j<22; j++) . When you delete a word in Name, you must not increment j .

The basic logic isn't too bad as long as you update the number of words in numNames and update j correctly.

UPDATE I just noticed that you have your indexes for i and j reversed in strcmp . That's another issue.

for (i = 0; i < numDelete; i++)
{
    for (j = 0; j < numName;)
    {
        if (strcmp(Name[j], Delete[i]) == 0)
        {
            for (k = j; k < numName - 1; k++)
            {
                strcpy(Name[k], Name[k+1]);
            }

            strcpy(Name[numName - 1], "");
            numName--; /* After deleting a name, reduce the size of the name array */
        }
        else
        {
            j++; /* Only increment j when not deleting. */
        }
    }
}

NOTE: I also got rid of flag it wasn't needed.

Answer 3

I also was able to solve the problem by doing it like the following:

len = 22;
for(i=0; i<5; i++)

{
    flag = 0;

for(j=0; j<len; j++)
{
    if(strcmp(Name[j],Delete[i]) == 0)
    {
        for (k = j; k<len-1; k++)
        {
            strcpy(Name[k],Name[k+1]);
        }

        strcpy(Name[len-1],"");
        len--;
    }
}
}