I supposed to perform a project which allocate N bytes of memory of struct person
and scanning f every person's name initial_money and some other variables
the problem for me when i run the code is that it is terminating at some point of taking input process and i don't why
also this problem faced me yesterday in code forces contest
#include <stdio.h>
#include <stdlib.h>
struct person
{
char name[15];
int initial_money;
int g;
int final_money;
int money;
};
int main()
{
int NP,i,j;
char target1[15];
scanf("%d",&NP);
struct person *p=malloc(NP*sizeof(struct person));
for(i=0;i<NP;i++)
{
scanf("%s",(p+i)->name);
}
for(i=0;i<NP;i++)
{
scanf("%s",target1);
for(j=0;j<NP;j++)
{
if((p+j)->name==target1)
{
scanf("%d%d",(p+j)->initial_money,(p+j)->g);
(p+j)->final_money=(p+j)->initial_money%(p+j)->g;
}
}
}
for(i=0;i<NP;i++)
{
printf("%s %d %d %d",(p+i)->name,(p+i)->initial_money,(p+i)->g,(p+i)->final_money);
}
return 0;
}
The scanf function need pointers for inputed values.
The line:
scanf("%d%d",(p+j)->initial_money,(p+j)->g);
Should be:
scanf("%d %d",&(p+j)->initial_money,&(p+j)->g);
When comparing strings you usually can't compare pointers directly:
if((p+j)->name==target1)
shoul be:
if(strcmp((p+j)->name, target1) == 0)
Related
i am facing some difficulties with malloc and structs. I want to read the m_data.number_chars as shown in my code (which is an integer) to be the memory that i want to allocate.. But when i compile my code, and run it, it crushes.. Any ideas..? Thanks in advance!
#include <stdio.h>
struct movies {
int number_chars;
char name;
int made_year;
float money;
};
struct movies m_data;
int main()
{
scanf("%d",&m_data.number_chars);
m_data.name=malloc(m_data.number_chars);
gets(m_data.name);
printf("%s",m_data.name);
}
Well you were supposed to pass char* to the scanf - more specifically address of the variable on which input will be stored. You didn't do that.
No return value check for the standard functions and ofcourse you didn't use malloc earlier.
#include <stdio.h>
#include <stdlib.h>
struct movies {
int number_chars;
char* name;
int made_year;
float money;
};
struct movies m_data;
int main(void)
{
if( scanf("%d",&m_data.number_chars)!= 1){
fprintf(stderr, "%s\n", "Error in input");
exit(EXIT_FAILURE);
}
getchar();
if(m_data.number_chars <= 0){
fprintf(stderr, "%s\n", "Error in number of character count");
exit(EXIT_FAILURE);
}
m_data.name = malloc(m_data.number_chars+1);
if(!m_data.name){
perror("Malloc error");
exit(EXIT_FAILURE);
}
if(fgets(m_data.name,m_data.number_chars+1,stdin)){
printf("[%s]\n",m_data.name);
}
return 0;
}
When calling scanf, you need to pass the address of the variable to hold the result (using the ampersand &). This would definitely cause serious memory problems right there.
Also, name is of type char. char is not a pointer. Therefore, you cannot assign the result of malloc() to name.
You need a pointer type.
Also, "crushes" is not a technical description of what is going wrong. You'll probably get further if you can articulate your situation better.
Try:
#include <stdio.h>
#include <stdlib.h>
struct movies {
int number_chars;
char *name;
int made_year;
float money;
};
struct movies m_data;
int main()
{
scanf("%d",&m_data.number_chars);
m_data.name=malloc(m_data.number_chars);
gets(m_data.name);
printf("%s",m_data.name);
free(m_data.name)
}
If we compared integers we would assign one of them as the largest/smallest one.
However, when I try comparing more than two strings, I can't manage assaigment.
In my code "for loop" compares two of the strings. This is good method but I need to compare one of them to the others individually. (I can predict that I need to use two for loop, but also I can't implement) What is your suggestions?
Here is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct wordSorting
{
char name[15];
int i = 0;
};
int main()
{
wordSorting *wordElement = (wordSorting *)malloc(sizeof(wordSorting));
wordElement = (wordSorting *)malloc(sizeof(wordSorting));
printf("-- Enter three person name --\n\n");
for (wordElement->i = 0; wordElement->i < 3; wordElement->i++)
{
printf("Enter %d. person name: ", wordElement->i + 1);
scanf("%s", wordElement[wordElement->i].name);
}
printf("\n");
for (wordElement->i = 0; wordElement->i < 3; wordElement->i++)
{
if ((strcmp(wordElement[wordElement->i].name, wordElement[wordElement->i + 1].name))<0)
{
printf("%s", wordElement[wordElement->i].name);
}
}
}
First
typedef struct wordSorting
{
char name[15];
int i = 0;
};
Members of typedef/struct cannot be initied.
That is not the way to define a typedef, change it as:
typedef struct
{
char name[15];
int i;
}wordSorting;
Second:
wordElement = (wordSorting *)malloc(sizeof(wordSorting));
makes no sense. malloc returns void pointer, and you already init your variable at the first element in the first line of code.
And, as someone edited: do not cast malloc return, please.
Third, :
wordSorting *wordElement = (wordSorting *)malloc(sizeof(wordSorting));
wordElement = (wordSorting *)malloc(sizeof(wordSorting));
printf("-- Enter three person name --\n\n");
for (wordElement->i = 0; wordElement->i < 3; wordElement->i++)
{
printf("Enter %d. person name: ", wordElement->i + 1);
scanf("%s", wordElement[wordElement->i].name);
}
You are allocating space for one element, no array are defined then wordElement[wordElement->i].name is undefined Behaviour.
Finally
I don't know what compiler are you using, but gcc cannot compile such a bad code full of errors...
Suggestion.
What I think you need is to use array, but you must allocate the number of member you need, by:
wordSorting *wordElement = malloc(sizeof(wordSorting)*num_of_elements);
or simply, using a local array:
wordSorting wordElement[num_of_elements];
Okay, so we're supposed to prompt a user to enter 25000 lines of text.
Each line contains three integers each. We are then to pass the third integer in that line to another struct, and connect each integer until you have 25000 interconnected integers.
Here's what I've tried:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct graph{
int begin;
int end;
int cost;
} PathEdge;
int comp_fcn(const void *a, const void *b) {
return ((PathEdge *) a)->cost - ((PathEdge *) b)->cost;
}
int main(void)
{
int nlines,i;
char r;
int ecost,ebegin,eend;
scanf("%d",&nlines);
PathEdge edges[nlines+1];
for(i=0;i<nlines;i++)
{
scanf("%d, %d, %dn",&ebegin, &eend, &ecost);
edges[i].begin = ebegin;
edges[i].end = eend;
edges[i].cost = ecost;
struct town
{
struct town *north;
int name[25000];
};
struct town *root, *current;
root = malloc(sizeof(struct town));
root->north = NULL;
strcpy (root->name,ecost);
current = malloc(sizeof(struct town));
current->north = root;
strcpy (current->name,ecost);
}
printf("Please enter a node that you want to examine. If you want to exit, please press 'X'.n");
scanf("%c",&r);
switch(r)
{
case 'X':
case 'x':
printf("You entered a wrong value. Gomen. Try againn.");
break;
default:
if((0<r)&&(r<25000))
{
printf("You have accessed node %dn",r);
printf("Its neighboring nodes are %dn",edges[r].cost);
printf("Its neighboring nodes are %dn",edges[i].cost);
}
else
{
printf("Invalid input again. Please do try again. Thanksn");
}
break;
}
return 0;
}
And there are warnings...
"passing argument 1 of strcpy from incompatible pointer type"
"passing argument 2 of strcpy makes pointer from integer without a cast"
expected char*__ restrict __ but argument is of type 'int'
plus when I inputted that 25000 lines of text, segmentation fault happens. Please help. Thank you!
strcpy is for copying strings (i.e. zero terminated byte char "arrays"), you maybe should use memcpy instead.
Or if you just want to assign a single integer to one element in the array, use plain assignment:
current->name[someIndex] = ecost;
Or, maybe you intend that thename member should be a string? Then you should be using an array of characters and not integers. And you need to convert integer values to strings, using e.g. sprintf:
sprintf(current->name, "%d", ecost);
you can convert the integer to string using itoa and copy the string into root->name.
char str[20];
itoa(ecost, str, 10);
strcpy(root->name, str);
You did not state your exact issue so I am assuming you are overwhelmed and in that case you should try partitioning your implementation into functions so that you can work on isolated problems instead of a web of interconnected problems.
Here is one example:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct graph {
int begin;
int end;
int cost;
} PathEdge;
const char * GenerateInput()
{
static char local[2000];
static int last = 0;
int a, b, c;
a = last++;
b = last++;
c = last++;
sprintf_s(local, 2000, "%i %i %i", a, b, c);
return local;
}
void PathEdgeInitializeFromString(PathEdge * edge, const char * str)
{
sscanf_s(str, "%d %d %dn", &edge->begin, &edge->cost, &edge->end);
}
void QueryAndPrint(PathEdge * edges, int edges_n)
{
printf("Enter a number from 1 to %i: ", edges_n);
int index = 0;
scanf_s("%i", &index);
--index;
if (index < 0 || !(index < (edges_n)))
printf("Error");
else
printf("%i, %i, %i\n", edges[index].begin, edges[index].cost, edges[index].end);
}
int main() {
PathEdge edges[25000];
for (int i = 0; i < 25000; ++i)
{
const char * line = GenerateInput();
PathEdgeInitializeFromString(edges + i, line);
}
QueryAndPrint(edges, 25000);
return 0;
}
I have an array with multiple structs. When i ask the user to enter data the first time everything works but when i ask again for the next position in the array the program crashes. If this method doesn't work souldn't the program crash in the beginning? Is something wrong with malloc?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct student {
char name[50];
int semester;
};
struct prof {
char name[50];
char course[50];
};
struct student_or_prof {
int flag;
int size;
int head;
union {
struct student student;
struct prof prof;
}
}exp1;
struct student_or_prof *stack;
void init(int n)
{
stack = malloc(n);
}
int push(struct student_or_prof **pinx,int *head,int n)
{
char name[50];
printf("\nn= %d\n",n);
printf("\nhead= %d\n",*head);
if(*head==n)
{
printf("Stack is full.\n");
return 1;
}
char x;
printf("Student or Professor? [s/p] ");
getchar() != '\n';
scanf("%c",&x);
if(x=='s')
{
getchar() != '\n';
pinx[*head]->flag = 0;
printf("\n\nGive student's name: ");
fgets(pinx[*head]->student.name,sizeof(pinx[*head]->student.name),stdin);
printf("\nGive student's semester: ");
scanf("%d",&(pinx[*head]->student.semester));
printf("\nName = %s\tSemester = %d",pinx[*head]->student.name,pinx[*head]->student.semester);
}
else if(x=='p')
{
getchar() != '\n';
pinx[*head]->flag = 1;
printf("\n\nGive professor's name: ");
fgets(pinx[*head]->prof.name,sizeof(pinx[*head]->prof.name),stdin);
printf("\nGive course: ");
fgets(pinx[*head]->prof.course,sizeof(pinx[*head]->prof.course),stdin);
printf("\nName = %s\tCourse = %s\n",pinx[*head]->prof.name,pinx[*head]->prof.course);
}
(*head)++;
printf("\nhead= %d\n",*head);
}
int main()
{
int n,i;
printf("Give size: ");
scanf("%d",&n);
init(n);
for(i=0;i<n;i++)
push(&stack,&exp1.head,n);
return 0;
}
You need to malloc the structure not n
malloc(sizeof(struct student_or_prof)*n)
EDIT:
And your code crashes again because pinx is a double pointer, so this operation is not valid:
pinx[*head]->flag = 0;
this is equivalent to:
*(pinx + *head)->flag = 0;
Since you are not changing what stack points to, you are better off using a single pointer instead of a double pointer.
So instead you should change your push API:
int push(struct student_or_prof *pinx,int *head,int n)
and call it like:
push(stack,&exp1.head,n);
malloc allocates the given number of bytes.
You have to multiply n with the size of your struct, to allocate enough memory.
pinx does not point to an array, so pinx[*head] is going to access invalid memory unless *head is zero.
I think you meant (*pinx)[*head] , which accesses the N-th element of the array you allocated via malloc. For example (*pinx)[*head].prof.name etc.
BTW, your head number doesn't seem to be used at all, except for exp1.head, maybe it'd be better to remove head from the struct, and just have a single variable head?
I am trying to get multiple entries for my struct via the keyboard. I think I am wrong inside of scanf but I am not sure where I am wrong. Thanks!
Here is what I have:
#include <stdio.h>
#include <math.h>
int main()
{
//define the structure
struct course
{
char title[20];
int num;
} ;
// end structure define
//define the variable
struct course classes;
printf("Enter a course title and course number");
scanf("%s %d", classes[3].title, &classes.num);
return 0;
}
Fix the code as Carl said and it works fine:
#include <stdio.h>
int main()
{
struct course
{
char title[20];
int num;
} ;
struct course class;
printf("Enter a course title and course number");
scanf("%s %d", class.title, &class.num);
printf("%s %d", class.title, class.num);
return 0;
}
There are a couple issues.
You have this struct called "classes", but it has only 1 entry - you're accessing the 3rd entry so you're running off the end.
Also, Title is 20 bytes long, but if you enter something larger in scanf(), it will just overflow. The basic scanf() structure looks ok though.
I would set it up more like this:
#include <stdio.h>
#include <math.h>
#define MAX_CLASSES 50 // how big our array of class structures is
int main()
{
//define the structure
struct course
{
char title[20];
int num;
} ;
// end structure define
//define the variable
struct course classes[MAX_CLASSES];
int nCurClass = 0; // index of the class we're entering
bool bEnterMore = true;
while (bEnterMore == true)
{
printf("Enter a course title and course number");
scanf("%s %d", classes[nCurClass].title, &classes[nCurClass].num);
// if user enters -1 or we fill up the table, quit
if (classes[nCurClass].num == -1 || nCurClass > MAX_CLASSES-1)
bEnterMore = false;
}
}
That's the basic idea. Another improvement that could be made would be checking the length of the course title before assigning it to classes[].title. But you need something to do ;-)