Problem with copying a string into array in a struct

This is a discussion on Problem with copying a string into array in a struct within the C Programming forums, part of the General Programming Boards category; Now the problem I have is that when I copy strings into an array in a struct, it does it, ...

  1. #1
    Cogito Ergo Sum
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    Problem with copying a string into array in a struct

    Now the problem I have is that when I copy strings into an array in a struct, it does it, but when I try to print the first element of the array in the struct it prints out everything that's in the array. I think you just need to look at the colour highlighted bits.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    #include <string.h>
    
    //3 AI's and 1 player game
    
    typedef struct player Player;
    
    struct player {
      
      char alias[25];    //player name
      char nCards[26];     //cards the player has
      Player *next;
    };
    
    int TCards;   //total cards
    
    Player *newn(void); //new node (player)
    //int cards (void);
    int dist (void);   //distributing
    
    int main (void) {
    
      dist();
    
      return 0;
    }
    
    int dist (void) {
      
      char *cards[] = {"2c","3c","4c","5c","6c","7c","8c","9c","10c","JC","QC","KC","AC",
                        "2s","3s","4s","5s","6s","7s","8s","9s","10s","JS","QS","KS","AS",
                        "2h","3h","4h","5h","6h","7h","8h","9h","10h","JH","QH","KH","AH",
                        "2d","3d","4d","5d","6d","7d","8d","9d","10d","JD","QD","KD","AD"};
      char *cards2[] = {"2c","3c","4c","5c","6c","7c","8c","9c","10c","JC","QC","KC","AC",
                        "2s","3s","4s","5s","6s","7s","8s","9s","10s","JS","QS","KS","AS",
                        "2h","3h","4h","5h","6h","7h","8h","9h","10h","JH","QH","KH","AH",
                        "2d","3d","4d","5d","6d","7d","8d","9d","10d","JD","QD","KD","AD"};
    
      /*char *p_dist[52]; //distributed cards are also copied into this array, so no recopying
      char *p_dist2[52];*/ //second array to handle doubles to prevent infinite loop from less-card distribution
    
      int i = 0; //indexer of array from distributor
      int j = 0;
      int arr_choice; //value can be 0 or 1, if 0, then take from cards[], if 1, from cards2[]
    
    
      Player *n_player;  //node for new players
      Player *user;      //human
      Player *ai_1;
      Player *ai_2;
      Player *ai_3;
    
      puts("Creating AI's and User...");
    
      n_player = newn();
      user = n_player;
      n_player = newn();
      ai_1 = n_player;
      n_player = newn();
      ai_2 = n_player;
      n_player = newn();
      ai_3 = n_player;
    
      puts("\nEnter your name");
      scanf("&#37;25s", user->alias);
      puts("\nEnter 1st AI's name");
      scanf("%25s", ai_1->alias);
      puts("Enter 2nd AI's name");
      scanf("%25s", ai_2->alias);
      puts("Enter 3rd AI's name");
      scanf("%25s", ai_3->alias);
    
    
      printf("\n\nDistributing cards to %s...\n\n", user->alias);
      srand ( time(NULL) );         //seed
      TCards = 0;  //indexer for controlling cards that go to user
    
    //////////////////*THIS IS THE DISTRIBUTION LOOP FOR THE HUMAN USER*/////////////////
      for (TCards=0; TCards < 25; TCards++){   //104 / 4 = 26 cards per user
        arr_choice = rand()/(int) (((unsigned)RAND_MAX + 1)/ 2);
        if(arr_choice == 0) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          strcpy(&user->nCards[j], cards[i]);
          cards[i] = "0";
          j++;
        }
        else if(arr_choice == 1) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards2[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          strcpy(&user->nCards[j], cards2[i]);
          cards[i] = "0";
          j++;
        }
      }
      int b = 0;
      [B]printf("%s\n", &user->nCards);
      return 0;
    }
    
    Player *newn(void) {
      
      Player *player;
      player = (Player*)malloc(sizeof(Player));
      
      return (player);
    }
    So essentially instead of the first element printing say: "2s"

    It will print 2s3dfJK3d...etc etc.

    I think it's because of the way I've used the pointers. How do I fix this?

    Thanks

    EDIT: Don't ask me why [b] comes before printf, it's not like that in the code, the formatting doesn't work too well when I tried editing here.
    Last edited by JFonseka; 04-30-2008 at 06:44 AM.
    =========================================
    Everytime you segfault, you murder some part of the world

  2. #2
    and the hat of int overfl Salem's Avatar
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    Perhaps you want
    char nCards[26][3];

    And
    printf("&#37;s\n", user->nCards[0] );
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    Code:
    >  char nCards[26];
    nCards need to be two dimensional, so you can store more than one card, each card being a string.
    Code:
      char nCards[26][3];

  4. #4
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    Why does it need to be [26][3] ? What is the [3] for ?

    The user gets only 26 cards, so isn't [26] enough for storing the cards? Where each card is indicated by a string, so 26 cards, 26 strings.
    =========================================
    Everytime you segfault, you murder some part of the world

  5. #5
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    You need [26] [3] because right now you have an array of 26 chars. What you want is an array of char-arrays, which is what they are suggesting. The 3 is so that the strings are null-terminated I guess.

    Or you could just get a array of char-pointers like:

    char* nCards[26];

  6. #6
    Cogito Ergo Sum
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    The two dimensional seems to work, but not properly, sometimes I get garbage values. I can't use char *nCards[26]

    That doesn't work.
    =========================================
    Everytime you segfault, you murder some part of the world

  7. #7
    CSharpener vart's Avatar
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    That doesn't work.
    You mean - you haven't found yet a correct way to make it work...
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  8. #8
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    Quote Originally Posted by vart View Post
    You mean - you haven't found yet a correct way to make it work...

    Not really, I tried that several times before with varying things, it didn't work, so I assumed it didn't.
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  9. #9
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    Quote Originally Posted by JFonseka View Post
    Not really, I tried that several times before with varying things, it didn't work, so I assumed it didn't.
    You assume wrong - there's certainly a way to make it work, because a 2D array can ALWAYS be replaced with an array of pointers - you obviously have to make the pointers point to some suitable memory, but it certainly can be done.

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  10. #10
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    Well I get segmentation faults that way, do I need to malloc before strcpy ?
    =========================================
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  11. #11
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    Did that too now, it works a lot better, except it randomnly segfaults sometimes.
    =========================================
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  12. #12
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    If you post the code, we will be much better equipped to help you.

    --
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    Please don't PM me for help - and no, I don't do help over instant messengers.

  13. #13
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    #include <string.h>
    
    //3 AI's and 1 player game
    
    typedef struct player Player;
    
    struct player {
      
      char alias[25];    //player name
      char *nCards[26];     //cards the player has
      Player *next;
    };
    
    int TCards;   //total cards
    
    Player *newn(void); //new node (player)
    //int cards (void);
    int dist (void);   //distributing
    
    int main (void) {
    
      dist();
    
      return 0;
    }
    
    int dist (void) {
    
      char *cards[] = {"2c","3c","4c","5c","6c","7c","8c","9c","Tc","JC","QC","KC","AC",
                        "2s","3s","4s","5s","6s","7s","8s","9s","Ts","JS","QS","KS","AS",
                        "2h","3h","4h","5h","6h","7h","8h","9h","Th","JH","QH","KH","AH",
                        "2d","3d","4d","5d","6d","7d","8d","9d","Td","JD","QD","KD","AD"};
      char *cards2[] = {"2c","3c","4c","5c","6c","7c","8c","9c","Tc","JC","QC","KC","AC",
                        "2s","3s","4s","5s","6s","7s","8s","9s","Ts","JS","QS","KS","AS",
                        "2h","3h","4h","5h","6h","7h","8h","9h","Th","JH","QH","KH","AH",
                        "2d","3d","4d","5d","6d","7d","8d","9d","Td","JD","QD","KD","AD"};
    
      /*char *p_dist[52]; //distributed cards are also copied into this array, so no recopying
      char *p_dist2[52];*/ //second array to handle doubles to prevent infinite loop from less-card distribution
    
      int i = 0; //indexer of array from distributor
      int j = 0;
      int arr_choice; //value can be 0 or 1, if 0, then take from cards[], if 1, from cards2[]
    
    
      Player *n_player;  //node for new players
      Player *user;      //human
      Player *ai_1;
      Player *ai_2;
      Player *ai_3;
    
      puts("Creating AI's and User...");
      // THINGS FINALLY STOPPED GIVING SEG FAULTS, CHECK SIZE OF ALLOCATION
      n_player = newn();
      user = n_player;
      n_player = newn();
      ai_1 = n_player;
      n_player = newn();
      ai_2 = n_player;
      n_player = newn();
      ai_3 = n_player;
    
      puts("\nEnter your name");
      scanf("&#37;25s", user->alias);
      puts("\nEnter 1st AI's name");
      scanf("%25s", ai_1->alias);
      puts("Enter 2nd AI's name");
      scanf("%25s", ai_2->alias);
      puts("Enter 3rd AI's name");
      scanf("%25s", ai_3->alias);
    
    
      printf("\n\nDistributing cards to %s...\n\n", user->alias);
      srand ( time(NULL) );         //seed
      TCards = 0;  //indexer for controlling cards that go to user
    
    //////////////////*THIS IS THE DISTRIBUTION LOOP FOR THE HUMAN USER*/////////////////
      for (TCards=0; TCards < 25; TCards++){   //104 / 4 = 26 cards per user
        arr_choice = rand()/(int) (((unsigned)RAND_MAX + 1)/ 2);
        if(arr_choice == 0) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          user->nCards[j] = malloc(strlen(cards[i])*sizeof(char*));
          strcpy(user->nCards[j], cards[i]);
          cards[i] = "0";
          j++;
        }
        else if(arr_choice == 1) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards2[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          user->nCards[j] = malloc(strlen(cards2[i])*sizeof(char*));
          strcpy(user->nCards[j], cards2[i]);
          cards[i] = "0";
          j++;
        }
      }
      int b;
      for (b=0;b<25;b++){
        printf("%s\n", user->nCards[b]);
      }  
    
    /////////////////////*THIS IS THE DISTRIBUTION LOOP FOR AI 1////////////////////
      printf("\n\nDistributing cards to %s...\n\n", ai_1->alias);
      j = 0;
      for (TCards=0; TCards < 25; TCards++){   //104 / 4 = 26 cards per user
        arr_choice = rand()/(int) (((unsigned)RAND_MAX + 1)/ 2);
        if(arr_choice == 0) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          ai_1->nCards[j] = malloc(strlen(cards[i])*sizeof(char*));
          strcpy(ai_1->nCards[j], cards[i]);
          cards[i] = "0";
          j++;
        }
        else if(arr_choice == 1) {
          i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          while(strcmp(cards2[i], "0") == 0) {
            i = rand()/(int) (((unsigned)RAND_MAX + 1)/ 53);
          }
          ai_1->nCards[j] = malloc(strlen(cards2[i])*sizeof(char*));
          strcpy(ai_1->nCards[j], cards2[i]);
          cards[i] = "0";
          j++;
        }
      }
      for (b=0;b<25;b++){
        printf("%s\n", ai_1->nCards[b]);
      }
      return 0;
    }
    
    Player *newn(void) {
      
      Player *player;
      player = (Player*)malloc(sizeof(Player));
      
      return (player);
    }
    =========================================
    Everytime you segfault, you murder some part of the world

  14. #14
    CSharpener vart's Avatar
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    nCards[j], is a pointer - you should not use strcpy just
    ai_1->nCards[j] = cards2[i];

    no need to malloc as well

    also char *cards2
    should be declared as
    const char *cards2
    as all other const char pointers used
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  15. #15
    CSharpener vart's Avatar
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    if instead of
    cards[i] = "0";
    you will use cards[i] = NULL;
    your check
    strcmp(cards2[i], "0") == 0
    could be made shorter:
    cards[i] == NULL
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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