Ordering strings in an array by length

This is a discussion on Ordering strings in an array by length within the C Programming forums, part of the General Programming Boards category; So for this program I have to have the user input 10 strings. Then the menu asks them how they ...

  1. #1
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    Oct 2010
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    16

    Ordering strings in an array by length

    So for this program I have to have the user input 10 strings. Then the menu asks them how they would like their strings outputted. The first two options (which are print the way they were input, and print in reverse order from how they were input) I have working properly. It's the third option that is giving me trouble.

    I need to print their strings descending from longest to shortest.
    i.e. if they input:
    aaa
    b
    cccccc
    dd

    it will output:
    cccccc
    aaa
    dd
    b

    The function I am using to do this is incorrect and I'm a bit lost now.

    Here is my code:

    Code:
    #include<stdio.h>
    #include<string.h>
    #include<stdbool.h>
    #include<stdlib.h>
    
    _Bool readLine(char *str, int maxLen);
    int array_compare(const void *a, const void *b);
    
    int main ()
    {
      char strs[10][80];
      int numStrs=0;
      int choice;
      int i;
      
      for (i=0; i<10; ++i)
      {
      readLine(strs[i], 80);
      }
      
        do
        {
        printf("1) Print list of strings in the order input.\n");
        printf("2) Print list of strings in the reverse order input.\n");
        printf("3) Print list of strings in order of length.\n");
        printf("4) Quit\n");
        scanf("%d", &choice);
    	
    	  if(choice==1) //print strings in order of input
    	  {
    	    for (i=0; i<10; ++i)
    	    printf("%s", strs[i]);
    	  
    	  printf("\n");
    	  }
    	
    	  if(choice==2) //print strings in reverse order of input
    	  {
    	    for (i=9; i>=0; --i)
    	    printf("%s", strs[i]);
    	  
    	  printf("\n");
    	  }
    	
    	  if(choice==3) //print strings in order of length
    	  {
          qsort(strs, 10, sizeof(char), array_compare);
    	    for(i=0; i<10; ++i)
    	    printf("%s", strs[i]);
    	
    	  printf("\n");
          }	
        }
    
        while(choice!=4 || choice <=0);
    	
    
    }
    
    _Bool readLine(char *str, int maxLen) //read in strings
    {
    int i=0;
    int c = 'a';
      for(i=0; c!='\n' && i<maxLen-1; ++i)
      {
      c= getchar();
        if(c==EOF)
         break;
    	 
    	 str[i]=c;
      }
      str[i]='\0';
    }
    
    int array_compare(const void *a, const void *b) //order strings by length
    {
    const int *pa = (const int*)a;
    const int *pb = (const int*)b;
    
    return *pa - *pb;
    }
    If anyone can show me how my function should look I would really appreciate it!! Thanks in advance!

  2. #2
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    Oct 2010
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    Oh, and I know there are variables I didn't use, sorry for any confusion regarding that.

  3. #3
    Registered User
    Join Date
    Sep 2006
    Posts
    8,868
    You can use a regular sorter for it, just change the comparison to:
    Code:
    char temp[biggerThanAnyStringYouHave];
    
    for(i=0;i<numStrings-1;i++) {
       for(j=i+1;j<numString;j++) {
          if((strlen(str[i]) > strlen(str[j])) {
            // swap the order of the strings using a temp string, and strcpy or memset
          }
       }
    }
    Last edited by Adak; 11-22-2011 at 05:08 PM.

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