I have to sort an array of structs with selection sort, after I read them from a file.txt.
My algorithm is not working as expected, but it always avoid to sort them and it print the struct in decreasing order.
Example of file.txt :
P0 "ANTONIO" 2000 4
P1 "BARTOLOMEO" 1995 6
P2 "CARLO" 2020 1
P3 "DEMETRIO" 1960 2
P4 "ETTORE" 1920 3
P5 "FRANCESCO" 1950 5
Input: 2 5 3 1 6 4
Output: 4 6 1 3 5 2
What am I doing wrong?
Code below:
#include <stdio.h>
#include <stdlib.h>
#define N 7
struct persona
{
char codice[10];
char nome[30];
int anno[10];
int reddito[10];
};
int main()
{
FILE* fp;
fp = fopen("Testo.txt", "r");
struct persona* persona = malloc(sizeof(struct persona) * N);
int i = 0;
int j = 0;
if (fp != NULL)
{
while (i < N-1)
{
fscanf(fp, "%s %s %s %s",
persona[i].codice,
persona[i].nome,
persona[i].anno,
persona[i].reddito);
i++;
}
}
else
{
perror("Errore");
}
fclose(fp);
for(i=0; i<N-2; i++)
{
int min = persona[i].reddito;
for(j=i+1; j<N-1; j++)
{
if(persona[j].reddito < persona[i].reddito)
{
min = persona[j].reddito;
}
persona[N] = persona[j];
persona[j] = persona[i];
persona[i] = persona[N];
}
}
for(i=0; i<N-1;i++)
{
printf("%s\t %s\t %s\t %s\n",
persona[i].codice,
persona[i].nome,
persona[i].anno,
persona[i].reddito);
}
}
You have 6 lines in the file, but you have defined N as 7. It should be updated to 6.
while (i < N-1)
You are reading the first N-2, that is, 5 lines from the file. The 6th line is not being read. Same goes for other loops in the code using N.
int anno[10];
int reddito[10];
You do not need integer array to read the numeric fields in file, an integer should suffice.
As mentioned by #WhozCraig in the comments, the selection sort algorithm is incorrect. Here's the updated code for reference:
#include <stdio.h>
#include <stdlib.h>
#define N 6
typedef struct persona
{
char codice[10];
char nome[30];
int anno;
int reddito;
} PERSONA;
int main()
{
FILE *fp;
if ((fp = fopen("file.txt", "r")) == NULL)
{
perror("\nFile not found");
exit(1);
}
PERSONA *persona = malloc(sizeof(struct persona) * N);
int i = 0, j;
while (i < N)
{ if (fscanf(fp, "%s %s %d %d", persona[i].codice, persona[i].nome, &persona[i].anno, &persona[i].reddito) == EOF) {
break;
}
i++;
}
fclose(fp);
PERSONA temp;
/* selection sort */
for (i = 0; i < N - 1; i++)
{
int jMin = persona[i].reddito;
for (j = i + 1; j < N; j++)
{
if (persona[j].reddito < persona[jMin].reddito)
{
jMin = j;
}
}
if (jMin != i)
{
temp = persona[i];
persona[i] = persona[jMin];
persona[jMin] = temp;
}
}
for (i = 0; i < N; i++)
{
printf("\n%s\t %s\t %d\t %d", persona[i].codice, persona[i].nome, persona[i].anno, persona[i].reddito);
}
}
Further improvements:
You could also calculate the number of lines in the file in the code instead of relying on a hardcoded value N.
The statement to check sets only the min only if this statement is true
if(persona[j].reddito < persona[i].reddito)
try using the qsort function
int cmpfunc (const void * a, const void * b) {
struct persona *p1 = (struct persona *)a;
struct persona *p2 = (struct persona *)b;
if(p1->reddito < p2->reddito) return -1;
if(p1->reddito > p2->reddito) return 1;
return 0;
}
and instead of the for loop, use
qsort(persona, N, sizeof(struct persona), cmpfunc);
Related
I have made one program, where you enter a few characters (10 max). It makes you a list, count average length of surnames, tell about how much different names. But the problem is, when I enter the last number (10) - it sorts me it incorrectly (like 39399349349, 3443993). Beneath I will present my code. I am newbie in C, so please don't shut on me) I am convinced that sorting function is incorrect, but don't know what exactly(
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct people {
int num[10];
char surname[20];
char name[10];
} peoples[10], c;
int compare_people_num(const void *a, const void *b);
int main()
{
int i, j, k = 0, l = 0, m = 0, n = 0;
float s = 0;
char str[100];
system("chcp 1251 > nul");
for (i = 0, j = 0; i < 10; i++, j++)
{
printf("Enter number, surname, name %d of your human: ", i + 1);
fgets(str, sizeof str, stdin);
sscanf(str, "%d %s %s", &peoples[j].num, &peoples[j].name, &peoples[j].name);
while (str[n] != '\n')
{
if (str[n] != ' ')
{
peoples[j].num[k] = str[n];
}
else
break;
n++;
k++;
}
n++;
k = 0;
while (str[n] != '\n')
{
if (str[n] != ' ')
{
peoples[j].surname[k] = str[n];
}
else
break;
n++;
k++;
}
n++;
k = 0;
while (str[n] != '\n')
{
if (str[n] != '\0')
{
peoples[j].name[k] = str[n];
}
else
break;
n++;
k++;
}
n = 0;
k = 0;
}
for (i = 0; i < 10; i++)
{
for (j = i + 1; j < 10; j++)
{
if (!strcmp(peoples[i].name, peoples[j].name))
m = 1;
}
if (m == 0)
l++;
m = 0;
s = s + strlen(peoples[i].surname);
}
for (i = 0; i < 9; i++)
for (j = 0; j < 9; j++)
if (strcmp(peoples[j].num, peoples[j+1].num) > 0)
{
qsort(peoples, 10, sizeof(struct people), &compare_people_num);
}
for (i = 0; i < 10; i++)
{
printf("%d ", peoples[i].num);
printf("%s ", peoples[i].name);
printf("%s ", peoples[i].surname);
printf("\n");
}
printf("\nYou have %d different names\n", l);
printf("Avarege lenght of surname is = %f\n", s / 10);
}
int compare_people_num(const void *a, const void *b)
{
const struct people *p1 = a;
const struct people *p2 = b;
return p1->num - p2->num; // Change order to reverse sort
}
I went through your code and removed things that weren't needed. In both your input and sorting, it seemed like you were doing things twice. I tried to document the changes I made and explain why they should be made.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// It's generally a good idea to use #define when you have some global constants
// I made some of the constants larger than what you showed to prevent issues
#define MAX_NAME_LEN 40
#define MAX_SURNAME_LEN 40
#define NUM_PEOPLE 10
#define BUFF_LEN 100
// Separate your struct...
struct person {
int num;
char name[MAX_NAME_LEN];
char surname [MAX_SURNAME_LEN];
};
// ... and array decleration
static struct person people[NUM_PEOPLE];
// I added this function, to make it easier to display a person
void print_person (const struct person * p) {
printf("Person %d %s %s\n", p->num, p->name, p->surname);
}
// This function will print out every person in the people array
void print_people (void) {
for (int i=0; i<NUM_PEOPLE; i++) {
print_person(&people[i]);
}
}
// Compares two people by number
int compare_people_num (const void * a, const void * b) {
struct person * p0 = (struct person *) a;
struct person * p1 = (struct person *) b;
return p0->num - p1->num;
}
// Compares two people by name
int compare_people_name (const void * a, const void * b) {
struct person * p0 = (struct person *) a;
struct person * p1 = (struct person *) b;
return strcmp(p0->name, p1->name);
}
int main (void) {
int i;
char buffer[BUFF_LEN];
for (i=0; i<NUM_PEOPLE; i++) {
printf("Enter number, surname, and name of person %d: ", i+1);
fflush(stdout); // fflush makes sure that our text is shown to the user
fgets(buffer, BUFF_LEN, stdin); // Read user input in to buffer
// It's unclear what you were doing here
// This sscanf line takes a line of text, and splits it into a number and two words
// It then stores that number in people[i].num, and stores the words in name and surname
// However, right after this, you have several while loops that appear to be manually doing the same
// thing all over again. If you want to read all of the input in, just the line below is enough
sscanf(buffer, "%d %s %s", &people[i].num, people[i].name, people[i].surname);
}
// We've read all of the people in now
// Uncomment the next line to check out the output at this state:
// print_people();
// To count names, we first need to sort the people by their name
// We do this using a qsort call
qsort(people, NUM_PEOPLE, sizeof(struct person), compare_people_name);
// Once the names are sorted, we'll calculate how many different names there are
// We start the count at 1, and start checking from the second person (index 1)
// This is because the first person will always be unqiue, and we can't compare to
// person negative 1
int n_names = 1;
for (i=1; i<NUM_PEOPLE; i++) {
char * current = people[i].name;
char * previous = people[i-1].name;
if (!strcmp(current, previous)) {
n_names ++;
}
}
// Now we have to sort the people based on their num field
// Again, in your code, it looked like you were doing this more than nessecary
// We just have to call qsort once, as such
qsort(people, NUM_PEOPLE, sizeof(struct person), compare_people_num);
// We will also do a loop through to calculate the average surname length
float avg_surname_len = 0;
for (i=0; i<NUM_PEOPLE; i++) {
avg_surname_len += (float)strlen(people[i].surname);
}
avg_surname_len /= (float)NUM_PEOPLE;
// We're all done! The people are sorted by number.
print_people();
printf("There are %d unique names\n", n_names);
printf("The average surnames is %f characters\n", avg_surname_len);
}
I'm trying to Heapsort (sort by Alphabetical Order the name of the phone) a structure of char array read from a txt file. My algorithm works for integer but when I change to 'char' type it don't show any result nor any error
Therefore I really dont know what's wrong with my code. Please help, I'm new to this.
My txt file
iPhone_XR 128 6.1 599
Galaxy_s20 256 5.8 599
oppo_find_x 128 4.7 429
iPhone_SE 128 4.0 349
My code
#include <stdio.h>
struct phone
{
char a[100];
char b[100];
char c[100];
char d[100];
};
struct phone array[100];
void swap(char *e, char *f)
{
char temp = *e;
*e = *f;
*f = temp;
}
void heapify(char arr[], int n, int i)
{
int largest = i;
int left = 2 * i + 1;
int right = 2 * i + 2;
if (left < n && arr[left] > arr[largest])
largest = left;
if (right < n && arr[right] > arr[largest])
largest = right;
if (largest != i)
{
swap(&arr[i], &arr[largest]);
heapify(arr, n, largest);
}
}
void heapSort(char arr[], int size)
{
for (int i = size / 2 - 1; i >= 0; i--)
heapify(arr, size, i);
for (int i = size - 1; i >= 0; i--) {
swap(&arr[0], &arr[i]);
heapify(arr, i, 0);
}
}
int main(void)
{
int size;
char ch;
int count = 0;
char A[1000];
FILE *myfile = fopen("phonedb.txt", "r");
if (myfile == NULL) {
printf("Cannot open file.\n");
return 1;
}
else {
do //count lines
{
ch = fgetc(myfile);
if (ch == '\n') count++;
} while (ch != EOF);
rewind(myfile);
// scan all the line inside the text
int i;
for (i = 0; i < count; i++) {
fscanf(myfile, "%s %s %s %s\n", array[i].a, array[i].b, array[i].c, array[i].d);
printf("%s %s %s %s\n", array[i].a, array[i].b, array[i].c, array[i].d);
}
}
heapSort(A, count);
printf("\nYour sorted list\n");
for (int i=0; i<size; i++)
{
printf("%s\n", array[i].a);
}
return 0;
}
Your program has lot of errors and some unnecessary use of char arrays.
But since you are sorting your data using phone names which is a string,
direct comparison won't work as it's not a primitive data type. You need to use library function strcmp() from <string.h> library.
Here's my working code.
#include<stdio.h>
#include<string.h>
struct phone
{
char phoneName[100];
int second,fourth;
float third;
};
struct phone array[100];
void swap(struct phone *e, struct phone *f)
{
struct phone temp = *e;
*e = *f;
*f = temp;
}
void heapify(struct phone arr[], int n, int i)
{
int largest = i;
int left = 2 * i + 1;
int right = 2 * i + 2;
if (left < n && strcmp(arr[left].phoneName, arr[largest].phoneName)>0)
largest = left;
if (right < n && strcmp(arr[right].phoneName, arr[largest].phoneName)>0)
largest = right;
if (largest != i)
{
swap(&arr[i], &arr[largest]);
heapify(arr, n, largest);
}
}
void heapSort(struct phone arr[], int size)
{
for (int i = size / 2 - 1; i >= 0; i--)
heapify(arr, size, i);
for (int i = size - 1; i >= 0; i--) {
swap(&arr[0], &arr[i]);
heapify(arr, i, 0);
}
}
int main()
{
int size;
char ch;
int count = 0;
FILE *myfile = fopen("phonedb.txt", "r");
if (myfile == NULL) {
printf("Cannot open file.\n");
return 1;
}
else {
do //count lines
{
ch = fgetc(myfile);
if (ch == '\n') count++;
} while (ch != EOF);
rewind(myfile);
// scan all the line inside the text
int i;
for (i = 0; i < count; i++) { // using floating point with 2 precision.
fscanf(myfile, "%s %d %f %d\n", array[i].phoneName, &array[i].second, &array[i].third, &array[i].fourth);
printf("%s %d %0.2f %d\n", array[i].phoneName, array[i].second, array[i].third, array[i].fourth);
}
}
heapSort(array, count);
printf("\nYour sorted list\n");
for (int i=0; i<count; i++)
{
printf("%s %d %0.3f %d\n", array[i].phoneName,array[i].second,array[i].third,array[i].fourth);
}
return 0;
}
And Here's the output:
iPhone_XR 128 6.10 599
Galaxy_s20 256 5.80 599
oppo_find_x 128 4.70 429
iPhone_SE 128 4.00 349
Your sorted list
Galaxy_s20 256 5.80 599
iPhone_SE 128 4.00 349
iPhone_XR 128 6.10 599
oppo_find_x 128 4.70 429
I have an university project in C programming. I ran into a problem with the following task. My program should order numbers in two arrays. In the first array i must save (the biggest of every fifth element) and that is my problem. I am not sure how to make the loop which reads five elements compare them, take the biggest one, and then continue doing this with the other elements. I am hoping someone to help because I blocked.
#define A 100
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
void show(int x[], int nx); //функция за показване на масивите
float vavedi(int x[], int nx); //функция, чрез която ръчно въвеждаме числата и ги обработваме
FILE* readFile(char* fname); //функция която чете файл и представя съдържанието му като масиви
int main()
{
int call, a = 0, b = 0, mode = 0, i = 0;
int check = 0;
char fail[A];
char* menu[] = {
"PROGRAM STARTED!",
"Enter an option:",
"1 : Write the numbers.",
"2 : Choose from a file.",
"0 : Exit."
};
do {
for (i = 0; i < 5; i++)
printf("%s\n", menu[i]);
check=scanf("%d", &mode);
if (check != 1)
printf("ERROR! Try again!");
switch (mode)
{
case 1: {
//в случай 1 числата се въведждат от потребителя
call = vavedi(a, b);
break;
}
case 2: {
//в случай 2 потребителя използва съществуващ файл
printf("Enter the path of the file you want to open:\n");
scanf("%s", fail);
call = readFile(fail);
if (call == NULL) {
printf("The file doesn't exist! Try again!\n");
}
break;
}
case 0:
break;
default:
{
printf("ERROR! Try again!\n");
}
}
} while (mode != 0);
printf("\nThe program ended!\n");
return 0;
}
void show(int x[], int nx)
{
int k;
for (k = 0; k < nx; k++)
{
printf("\n Element[%d]= %d", k, x[k]);
}
}
float vavedi(int x[], int nx)
{
int call=0;
int enter=0;
int imin, max;
int b[A], c[A];
int i, j, j1, count;
j = 0;
do {
printf("\nCount of the elements:");
scanf("%d", &count);
if (count <= 0 || count > 100)
printf("Invalid input! Try again!\n");
} while (count <= 0 || count > 100);
for (i = 0; i < count; i++)
{
printf("\nEnter an element:");
scanf("%d", &c[i]);
}
printf("\n");
return enter;
}
Update : Including header file mentioned by #pmg.
If i understand correctly, your problem is to find largest element for every five elements:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <limits.h> // Put this after your header files
..
.. //Rest of the code.
..
for (i = 0; i < count; i++)
{
printf("\nEnter an element:");
scanf("%d", &c[i]);
}
size_t size = ceil(count/5.0);
memset(b , INT_MIN , size);
for(int i = 0 ; i < count ; i++)
{
b[i/5] = b[i/5] > c[i] ? b[i/5] : c[i];
}
// Print b like this:
for(i = 0 ; i < size; i++)
printf("%d" , b[i] );
Let's see how this works for array of size 9. array's indices will go from 0 to 8 . If I divide each of them by 5, I get 0 for i = 0 to 4 and 1 for i = 5 to 8. Now we can take max over elements in buckets of 5. You seem to be a beginner, hope this helps you in creating better understanding.
The other problem is the following:
{
int c[A], b[A];
int i = 0, j = 0, k = 0, num;
FILE* fp= NULL; //указател за файл
fp = fopen(fname, "r");
if (fp)
{
while (fscanf(fp, "%d", &c[i]) != EOF)
i++;
num=i;
size_t size = ceil(num/5.0);
memset(b , INT_MIN , size);
for(i = 0 ; i < num ; i++)
{
b[i/5] = b[i/5] > c[i] ? b[i/5] : c[i];
}
printf("\nARRAY1:\n");
for(i = 0 ; i < size; i++)
{
buble(b, i);
printf(" Element[%d]=%1d\n", i, b[i]);
}
printf("\nARRAY2:");
buble(c, num);
show(c, num);
printf("\n");
}
fclose(fp);
return fp;
}
It doesn't calculate the rigth way.
I have an input file a.txt:
1 abc 3
2 efgh 4.5
3 text 3
4 xyz 2
So basically, it has 3 columns, first one is int, second is text, and third is double. I need to read this file by rows (which actually works, I guess), but have some problems with writing only second and third column to another (b.txt) file. fprinft saves something like this:
0.000000
0.000000
0.000000
0.000000
xvæ$ 0.000000
instead of
abc 3
efgh 4.5
text 3
xyz 2
I simply need to save only the second and the third column from a.txt file to b.txt file. Here's my code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct mypair
{
char string[1024];
double number;
} mypair;
void zero_string(char *string, int n)
{
int i;
for(i=0; i<n; i++)
string[i] = '\0';
}
int row(FILE* f, struct mypair *p)
{
int num;
if(!feof(f))
{
if(fscanf(f,"%d %s %lf", &num, p->string, &p->number) == 3)
{
return 0;
}
}
else
{
return 1;
}
}
int main(int argc, char **argv)
{
int n = 5, status = 0, i = 0, j;
struct mypair array[5];
char file_in_name[255];
char file_out_name[255];
FILE *fin;
FILE *fout;
zero_string(file_in_name, 255);
zero_string(file_out_name, 255);
printf("Data file:\n> ");
scanf("%s", file_in_name);
printf("Out file:\n> ");
scanf("%s", file_out_name);
fin = fopen(file_in_name, "r");
fout = fopen(file_out_name, "w");
if( fin == NULL )
{
exit(-1);
}
if( fout == NULL )
{
exit(-1);
}
while(status != 1)
{
status = row(fin, &array[i]);
i ++;
fprintf(fout, "%s %lf\n", array[i].string, array[i].number);
if(i >= n)
break;
}
fclose(fin);
fclose(fout);
for(j=0; j<i; j++)
printf("%s %lf\n", array[i].string, array[i].number);
return 0;
}
I modified the code, now it works, thanks!
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct mypair
{
char string[1024];
double number;
} mypair;
void zero_string(char *string, int n)
{
int i;
for(i=0; i<n; i++)
string[i] = '\0';
}
int row(FILE* f, struct mypair *p)
{
int num;
if(!feof(f))
{
if(fscanf(f,"%d %s %lf", &num, p->string, &p->number) == 3)
{
return 0;
}
}
else
{
return 1;
}
}
int main(int argc, char **argv)
{
int n = 5, status = 0, i = 0, j;
struct mypair array[5];
char file_in_name[255];
char file_out_name[255];
FILE *fin;
FILE *fout;
zero_string(file_in_name, 255);
zero_string(file_out_name, 255);
printf("Data file:\n> ");
scanf("%s", file_in_name);
printf("Out file:\n> ");
scanf("%s", file_out_name);
fin = fopen(file_in_name, "r");
fout = fopen(file_out_name, "w");
if( fin == NULL )
{
exit(-1);
}
if( fout == NULL )
{
exit(-1);
}
printf("\n");
while(status != 1)
{
status = row(fin, &array[i]);
if(i >= n)
break;
else
{
if(status != -1)
fprintf(fout, "%s %lf\n", array[i].string, array[i].number);
}
i ++;
}
fclose(fin);
fclose(fout);
for(j=0; j<i; j++)
printf("%s %lf\n", array[j].string, array[j].number);
return 0;
}
In your bottom loop, you want to index your array by j, not i.
My text file is as following:
Random Words //this only appears once at the top
Occupation1
1 2 3 4 5
6 7 8 9 10
Occupation2
11 12 13 14 15
16 17 18 19 20
I am having some trouble with the input and was wondering if you could take a look at my code.
typedef struct foo
{
char occupation[256];
int numbers[limita][limitb];
}FOO;
void function(FOO input[]);
int main()
{
FOO input[limit];
function(input);
return 0;
}
void function(FOO input[])
{
FILE* file;
file = fopen("textfile.txt","r");
int a=0; int b =0;
char temp[81];
char randomwords[81];
while(fgets(temp,sizeof(temp)-1,file))
{
sscanf(temp, "%[^\n] %[^\n] %d", randomwords,&input[a].occupation[a], &input[a].numbers[a][b]);
a++;
}
}
So I tried printing out (with printf) the random words and the occupation but to no avail. I don't think i'm using numbers correctly at all as it has to be a 2D array and don't seem to be changing the columns.
I would really appreciate a step in the right direction/some help. Please explain simply. Thank you very much.
EDIT:
technomage brought up an interesting point regarding what i'm doing vs what I want. I'm not sure how to change in reflection to what he suggested though.
You probably want to do something like this. This implementation assumes that there are no blank lines in the input file. There are lot of hard coding here, you may want to make it better. I hope this helps you...
typedef struct foo
{
char occupation[256];
int numbers[2][5];
}FOO;
void function(FOO input[]);
void function(FOO input[])
{
FILE* file;
file = fopen("textfile.txt","r");
int a = 0, count, i;
char temp[81];
char randomwords[81];
if (file == NULL)
{
return;
}
fscanf(file, "%[^\n]\n", randomwords);
printf("%s\n", randomwords);
while (feof(file) != EOF)
{
i = 0;
i = fscanf(file, "%[^\n]\n", input[a].occupation);
if (i == -1)
break;
for (count=0; count < 5; count++)
{
i = 0;
i = fscanf(file, "%d", &(input[a].numbers[0][count]));
}
for (count=0; count < 5; count++)
{
i = 0;
i = fscanf(file, "%d", &(input[a].numbers[1][count]));
}
a++;
i = 0;
i = fscanf(file, "\n");
if (i == -1)
break;
};
fclose(file);
}
int main(int argc, char *argv[], char *envp[])
{
int i, j, count;
FOO input[10];
function(input);
for (count = 0; count < 2; count++)
{
printf("%s\n", input[count].occupation);
for (i = 0; i < 2 ; i++)
{
for (j = 0 ; j < 5 ; j ++)
{
printf ("%d ", input[count].numbers[i][j]);
}
printf ("\n");
}
printf ("\n");
}
}