Thread: passing a string from one variable to another

hello, im trying to write a program that involves me needing to be able to arrange a bunch of names in a specific order that have been scanned from a file.

the exact order is determined by a function i wrote that compares a bunch of numerical values as show:

Code:

void sort(double ppg[999], int numPlayers) {
  int y, x;
                                               // These keep it within range of datafile
    for (x = numPlayers - 1; x > 0; x = x - 1)
      for (y = 0; y < x; y = y + 1)
        if (ppg[y] < ppg[y+1])          // Compare size of integers
          swap(&ppg[y], &ppg[y+1]);
  }

void swap(double *a, double *b) {

  double temp;
  temp = *a;
  *a = *b;
  *b = temp;

}

this code just compares two numbers and swaps them based on which is greater. however, a lot of the data i have to swap is strings of first names, last names etc..

so i was wondering if anyone knows how i could transfer the string in one variable into a second variable (to basically get the same effect as switching numbers)

i tried this:

Code:

void charswap(char *c[20], char *d[20]) {

  char temp[20];
  temp = *c;
  *c = *d;
  *d = temp;

}

but i got an error and i dont think strings can simply be set to equal a different variable to swap them the same way as a number would.

so does anyone know how to pass a string from one variable to another?

hmmm, it makes a lot of sense. i updated it to:

Code:

void swap(double *a, double *b) {

  double temp;
  temp = *a;
  *a = *b;
  *b = temp;

}

void charswap(char c[20], char d[20])
{
  char temp[20];
  strcpy(temp, c);
  strcpy(c, d);
  strcpy(d, temp);
}

//-------------------------------------------------------------
// Function that will compare which variable is larger than the
// others and swap if true
//-------------------------------------------------------------

void sort(double ppg[999], int numPlayers, int games_played[999], int goals[999], int assissts[999],
  int points[999], char first_names[999], char last_names[999], char team_name[999], char position [999]) {
  int y, x;
                                               // These keep it within range of datafile
    for (x = numPlayers - 1; x > 0; x = x - 1)
      for (y = 0; y < x; y = y + 1)
        if (ppg[y] < ppg[y+1])          // Compare size of integers
          swap(&ppg[y], &ppg[y+1]);
          swap(&games_played[y], &games_played[y+1]);
          swap(&goals[y], &goals[y+1]);
          swap(&assissts[y], &assissts[y+1]);
          swap(&points[y], &points[y+1]);
          charswap(first_names[y], first_names[y+1]);
          charswap(last_names[y], last_names[y+1]);
          charswap(team_name[y], team_name[y+1]);
          charswap(position[y], position[y+1]);
  }

and then i go to call on it with this:

Code:

 sort(ppg, numPlayers, points, goals, assissts, games_played, first_names, last_names, team_name, position);

but i get about 12 different error messages saying

passing argument 1 of charswap makes poitner from integer without a cast

and

passing argument 7/8/9 of sort from incompatible pointer type

i tried playing around with the functions like adding pointers to the charswap function but it didnt change anything

Your code had an index array in it, why not sort with that?

Code:

/*
Daniel Sedin VAN L 73 38
Steven Stamkos TBL C 72 43
Henrik Sedin VAN C 73 18
Martin StLouis TBL R 72 26
Corey Perry ANA R 72 39
Alex Ovechkin WSH L 73 29
Henrik Zetterberg DET L 73 21
Jonathan Toews CHI C 70 30
Anze Kopitar LAK C 73 25
Jarome Iginla CGY R 75 33
Patrick Sharp CHI L 71 34
Brad Richards DAL C 62 25
Teemu Selanne ANA R 63 22
Sidney Crosby PIT C 41 32


*/


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

#define MAX 14

void sort(int index[MAX], char fname[][22], int key);

int main(void) {

  int i = 0, j, got, len, index[MAX];
  char fname[MAX][22];
  char lname[MAX][22];
  char team[MAX][4];
  char plays[MAX];
  int  data[MAX][2];
  

  FILE *fp;

  printf("\n\n");
  if((fp=fopen("team.dat","r")) == NULL) {
    printf("Error opening data file\n");
    return 0;
  }

  while(1) { //giving fscanf() it's own line
    got = fscanf(fp,"%s %s %s %c %d %d", fname[i],lname[i],team[i],&plays[i],&data[i][0],&data[i][1]); 
    if(got < 6)
      break;
 
    index[i] = i;  //you're building an index array at the same time? Good!    
    ++i; //welcome to C! :)     = i + 1;
    
  }
  //i has just counted the number of names in the array, so it can be used:

  printf("\n\n");
  for (j = 0; j < i; j++) {  //start with 0 not 1
    printf("%s %s %s %c %d %d\n",fname[j],lname[j],team[j],plays[j],data[j][0],data[j][1]);
  }

  sort(index, fname,1);
  printf("\n\n");
  for (j = 0; j < MAX; j++) {  //start with 0
    i = index[j];    
    printf("%11s   %-11s %4s  %c  %2d  %2d\n",fname[i],lname[i],team[i],plays[i],data[i][0],data[i][1]);
  }


  fclose(fp);
  printf("\n\n\t\t\t    press enter when ready");
  (void) getchar();
  return 0;
}
void sort(int index[MAX], char fname[][22], int key) {
  int i, j, temp;
    
  if(key==1) { //sort by first name
    /* This is substitution sort - similar to 
    bubble sort, but slightly faster
    */
    for(i=0;i<MAX-1;i++) {
      for(j=i+1;j<MAX;j++) {
        /*compare strings i with j, using the index numbers
          no actual data is swapped out, with this index sort
        */

        if(strcmp(fname[index[i]], fname[index[j]]) > 0) {
          temp = index[i];
          index[i] = index[j];
          index[j] = temp;
        }
      }
    } 
  }
  else if(key == 2) {
    //etc.
  }
}