How do I scan in an N number of strings (using structs) and then output that list of strings in reverse? - c++

Question

Using the specific struct below,
struct Student
{
char first[50];
char last[50];
char id[20];
};
How do I scan in an N number of strings consisting of first name, last name and ID number and then output that entire list backwards?
For example:
Input:
3
Dent Arthur 12345ABC
Prefect Ford 54321CBA
McMillan Tricia AB9876
Output:
McMillan Tricia AB9876
Prefect Ford 54321CBA
Dent Arthur 12345ABC
Here's what I have so far
#include <stdio.h>
#include <string.h>
struct Student
{
char first[50];
char last[50];
char id[20];
};
int main( )
{
int N, i;
scanf("%d", &N);
struct Student NAME;
for(i=0; i<N; i++){
scanf("%s %s %s", NAME.first[i], NAME.last[i], NAME.id[i]);
}
/*struct Student prefect;
scanf("%s %s %s", &prefect.first, &prefect.last, &prefect.id);
struct Student mcmillan;
scanf("%s %s %s", &mcmillan.first, &mcmillan.last, &mcmillan.id);*/
printf("\n");
printf("%s %s %s\n", NAME.first[i], NAME.last[i], NAME.id[i]);
printf("%s %s %s\n", NAME.first[i], NAME.last[i], NAME.id[i]);
printf("%s %s %s\n", NAME.first[i], NAME.last[i], NAME.id[i]);
return 0;
}

Answer 1

If you want to print the list (array) in a reverse manner,
for(i=N-1; i>=0; i--){
printf("%s %s %s\n", NAME.first[i], NAME.last[i], NAME.id[i]);
}
This fixes the reversing problem, although there is one more problem in the code. You have declared the members of struct to be of type string, and in the main function, you treat them as an array of strings. This won't work. You probably wanted to have an array of struct objects. This is how to go about it:
#include <stdio.h>
#include <string.h>
struct Student
{
char first[50];
char last[50];
char id[20];
};
int main( )
{
int N, i;
scanf("%d", &N);
struct Student NAME[10];
for(i=0; i<N; i++){
scanf("%s %s %s", NAME[i].first, NAME[i].last, NAME[i].id);
}
/*struct Student prefect;
scanf("%s %s %s", &prefect.first, &prefect.last, &prefect.id);
struct Student mcmillan;
scanf("%s %s %s", &mcmillan.first, &mcmillan.last, &mcmillan.id);*/
printf("\n");
for(i=N-1; i>=0; i--){
printf("%s %s %s\n", NAME[i].first, NAME[i].last, NAME[i].id);
}
return 0;
}
Link to ideone: http://ideone.com/hgPjjn

Answer 2

suggest modifying the struct to include a 'previous' and 'next' pointers
and putting the structs into a linked list.
perhaps by malloc'ing the struct instances, as each data becomes available.
linking the malloc'd struct onto the end of the linked list.
then to output,
walk down to the end of the list
then
printing current value,
step to previous list entry,
print value, etc
until back at the head pointer for the list.
could also insert each struct entry at the beginning of
the linked list,
that would avoid having to walk down the list
to find the last struct, before being able to print

Answer 3

You have made a bit error while tacking the students from console. First of all for taking the all student you have to create a array of struct Student-
struct Student students[100];
Then you may take the input from the user like this -
for(i=0; i<N; i++){
scanf("%s %s %s", students[i].first, students[i].last, students[i].id);
}
And after that all things remain same.When we write the complete code it would be -
#include <stdio.h>
#include <string.h>
struct Student
{
char first[50];
char last[50];
char id[20];
};
int main( )
{
int N, i;
scanf("%d", &N);
struct Student students[100];
for(i=0; i<N; i++){
scanf("%s %s %s", students[i].first, students[i].last, students[i].id);
}
printf("\n");
for(i=N-1; i>=0; i--){
printf("%s %s %s\n", students[i].first, students[i].last, students[i].id);
}
return 0;
}

Answer 4

This will work
#include <stdio.h>
#include <string.h>
struct Student {
char first[50];
char last[50];
char id[20];
};
int main() {
int N, i;
scanf("%d", &N);
struct Student NAME[N];
for (i = 0; i < N; ++i)
scanf("%s %s %s", NAME[i].first, NAME[i].last, NAME[i].id);
printf("\n");
for (i = N - 1; i >= 0; --i)
printf("%s %s %s\n", NAME[i].first, NAME[i].last, NAME[i].id);
return 0;
}