Please tell me what's wrong with this code.
Program to input number of students, their names and then print their names.
#include <stdio.h>
int main() {
int n, i;
scanf("%d", &n); // number of students
char* names[n]; // array of pointers.
for(i = 0; i < n; i++) {
scanf("%100[^\n]", names[i]); //student names
}
for(i = 0; i < n; i++){
printf("%s", names[i]); // printing students names
}
}
It does not show any error on compiling but it does not work.
Related
I trying to copy Char array elements to Int type array.... I defined size as 10 but when i put 10 character (a ~ j),the code is stop and get out from running...
#include <stdio.h>
#define size 10
int main(void){
char charr[size];
printf("input your string\n");scanf("%s", charr);
printf("%s", charr);
int arr[size];
for(int i = 0; i<size; i++){
arr[i] = (int)charr[i];
}
printf("\n");
for (int i = 0; i < size; i++){
printf("%d ", arr[i]);
}
return 0;
}
I want to copy my array over to a pointer, so I can sort the array without changing the original. I'm not getting any errors, and am at a dead end. I've tried printing the pointer's contents, but it's always junk data. If anyone could help me it'd be much appreciated.
#include <stdio.h>
void bubbleSort(char *array[], int arrIndex);
void displaySort (char *array[], int arrIndex);
int main (void)
{
int index;
int count = 0;
printf("Enter number of people (0 - 50): ");
scanf("%d", &index);
index -= 1;
char userLastFirst[25][index];
int userAge[index];
//defining pointer
char *namePtr[25][index];
//do while loop, loops while count is less than or equal to the index
do{
printf("Enter name %d (last, first): ", count);
scanf(" %[^\n]s", userLastFirst[count]);
printf("Enter age %d: ", count);
scanf("%d", &userAge[count]);
// printf("\n\n%s %d\n\n", userLastFirst[count], userAge[count]);
count++;
} while (count <= index);
//assigning values to pointer
for(int i = 0; i < index; i++){
namePtr[25][i] = &userLastFirst[25][i];
}
//does not print values of pointer
for(int i = 0; i < index; i++){
printf("value of ptr[%d] = %s\n", i, namePtr[i]);
}
bubbleSort(*namePtr, index);
displaySort(*namePtr, index);
return 0;
}
void bubbleSort(char *array[], int arrIndex)
{
for (unsigned int pass = 0; pass < arrIndex - 1; ++pass) {
for (int i = 0; i < arrIndex - 1; ++i) {
if (array[i] < array[i + 1]) {
int temp = *array[i];
*array[i] = *array[i + 1];
*array[i + 1] = temp;
}
}
}
}
void displaySort(char *array[], int arrIndex)
{
for(int i = 0; i < arrIndex; i++){
printf("%s",*array[i]);
}
}
Sorry it's a lot, but I've looked everywhere, and am not exactly sure what the problem is. I suspect it's how I pass pointers thru the functions, or how I'm using * and & but am not totally sure what I'm doing wrong. The for loop below the one that assigns the array values to the pointer is for testing. It's supposed to print out the values I had given it in the previous for loop, but it doesn't. It just prints junk data.
There are couple of issues here, and since I don't know what exactly you want your final code to look like, I am going to give a few examples of what is wrong and how you could possibly fix that.
char userLastFirst[25][index];
This should be
char userLastFirst[index][25];
You don't want 25 people with names up to index characters in them, but rather index people with names up to 25 characters int them.
char *namePtr[25][index];
should be
char namePtr[index][25];
Same as before + you don't need the * here. Since you decided to go with vla let's stick with it. You would use * and more specifically char ** if you went with malloc/calloc.
namePtr[25][i] = &userLastFirst[25][i];
rather than doing this awkward copying, try:
strcpy(namePtr[i], userLastFirst[i]);
it copies the entire string for you, rather than just a single character. You will need to #include the <string.h> library for that.
void bubbleSort(char *array[], int arrIndex)
The first bubble sort argument should be:
char array[][25] // the same in displaySort
if you want to do it without the hassle of malloc/calloc.
And also don't go with int as your temp type. Rather do char temp[25] and copy them around with strcpy.
And don't compare strings with <, it doesn't work in C. Use strcmp for that.
And that's it for doing it without malloc/calloc, here's an example code:
#include <stdio.h>
#include <string.h>
void bubbleSort(char array[][25], int size);
void displaySort(char array[][25], int size);
int main (void)
{
int num_of_people;
printf("Enter number of people (0 - 50): ");
scanf("%d", &num_of_people);
char original_array[num_of_people][25];
char copied_array[num_of_people][25];
for (int i = 0; i < num_of_people; i++) {
printf("Enter name %d (last, first): ", i);
scanf(" %[^\n]s", original_array[i]);
}
for(int i = 0; i < num_of_people; i++){
strcpy(copied_array[i], original_array[i]);
}
bubbleSort(copied_array, num_of_people);
displaySort(copied_array, num_of_people);
return 0;
}
void bubbleSort(char array[][25], int size)
{
for (int i = 0; i < size - 1; ++i) {
for (int j = 0; j < size - 1 - i; ++j) {
if (strcmp(array[j], array[j + 1]) > 0) {
char temp[25];
strcpy(temp, array[j]);
strcpy(array[j], array[j + 1]);
strcpy(array[j + 1], temp);
}
}
}
}
void displaySort(char array[][25], int size)
{
for(int i = 0; i < size; i++){
printf("%s\n",array[i]);
}
}
and the program work like this:
Enter number of people (0 - 50): 4
Enter name 0 (last, first): Kowalski, Jan
Enter name 1 (last, first): Kowalska, Anna
Enter name 2 (last, first): Nowak, Miłosz
Enter name 3 (last, first): Amper, Ohm
Amper, Ohm
Kowalska, Anna
Kowalski, Jan
Nowak, Miłosz
I hope this is something you wanted to achieve.
I wrote a simple program to take names and numbers from the user and store it in an array, then compare between each cell until it reach the maximum grade then it displays it. The problem is that when it run it shows a message (segmentation fault (Core dump)). I really don't know what my mistake is.
#include <stdio.h>
int main() {
int n;
printf("Enter the number of students: ");
scanf("%d", & n);
char name[n];
float score[n];
for (int i = 0; i < n; i++) {
printf("\nEnter the name of Student: ");
scanf("%s", & name[i]);
printf("\nEnter the score: ");
scanf("%f", & score[i]);
}
float max;
int index;
max = score[0];
index = 0;
for (int i = 1; i < n; i++) {
if (max < score[i]) {
max = score[i];
index = i;
}
}
printf("\nHighest mark scored is %f by student %s", name[index], score[index]);
}
1- you use user input to define the size of an array (wrong)
-- array in c has static size so you must define it's size before the code reach the compiling stage(use dynamic memory allocation instead)
2- scanf("%s", & name[I]); you want to save array of char and save the address at the name variable but name it self not a pointer to save address it's just of char type (wrong)
-- you need pointer to save the address of every name so it's array of pointer and a pointer to allocate the address of the array to it so it's a pointer to poiner and define max size of word if you define size the user input exceed it will produce an error
3- finally you exchanged the %f,%s in printf
#include <stdlib.h>
#include <stdio.h>
#define SIZE_OF_WORD 10
int main() {
int n;
printf("Enter the number of students: ");
scanf("%d", & n);
char **name=(char**)malloc((sizeof(char*)*n));
for (int i = 0; i < n; i++) {
name[i]=(char*)malloc((sizeof(char)*SIZE_OF_WORD));
}
float *score=(float*)malloc((sizeof(float)*n));
for (int i = 0; i < n; i++) {
printf("\nEnter the name of Student: ");
scanf("%s", name[i]);
printf("\nEnter the score: ");
scanf("%f", & score[i]);
}
float max;
int index;
max = score[0];
index = 0;
for (int i = 1; i < n; i++) {
if (max < score[i]) {
max = score[i];
index = i;
}
}
printf("\nHighest mark scored is %s by student %.0f\n", name[index],score[index]);
}
I want to make a simple variable for number of the round for a loop, so I tried my code
int size,counter,marks[size];
scanf("enter %d/n",&size);
for(counter=0;counter<size;counter++)
{
scanf("%d",&marks[counter]);
}
and compiled with no error but in run, it just shows "process returned -1073741571 <0*c00000FD>.
so I tried gets function and it shows "too many arguments to function 'gets' ".
int size;
int counter;
int marks[size];
scanf("enter %d/n",&size);
for(counter=0;counter<size;counter++)
{
gets("%d",&marks[counter]);
}
I'm using code::blocks 17.12 and the gnu compiler.
size can have any value when the array marks is allocated because it is not initialized. The array might be smaller than the entered size and so marks are stored in non-allocated memory, giving you the error.
This is a possible solution, but it doesn't compile with strict ISO C90. Presumably your CodeBlocks uses GCC that accepts variable length arrays and mixed declarations and code.
#include <stdio.h>
int main(void) {
int size;
printf("enter size: ");
scanf("%d",&size);
int marks[size];
int counter;
for (counter = 0; counter < size; counter++) {
scanf("%d", &marks[counter]);
}
for (counter = 0; counter < size; counter++) {
printf("%d: %d\n", counter, marks[counter]);
}
return 0;
}
BTW, please don't say "build error" if you have a runtime error. ;-)
Please don't use gets. It's dangerous.
As for your error in the scanf example, the first problem is the line
int size,counter,marks[size];
which declares marks with the uninitialized size value. Try initializing size first, then declaring the marks array.
Your second problem is scanf formatting string. Use scanf to read formatted input, not output a prompt. Use puts or printf for that.
Here's a full example:
#include <stdio.h>
int main(void) {
int size;
printf("Enter a size value: ");
scanf("%d", &size);
int marks[size];
for (int i = 0; i < size; i++) {
printf("Enter element %d: ", i);
scanf("%d", &marks[i]);
}
printf("You entered: ");
for (int i = 0; i < size; i++) {
printf("%d ", marks[i]);
}
puts("");
return 0;
}
Here's a sample run:
Enter a size value: 4
Enter element 0: 88
Enter element 1: 77
Enter element 2: 66
Enter element 3: 55
You entered: 88 77 66 55
If you're writing ANSI C-compatible code you can use dynamic memory with malloc:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int i, size, *marks;
printf("Enter a size value: ");
scanf("%d", &size);
if (size < 1) {
fprintf(stderr, "Invalid size specified\n");
exit(1);
}
marks = malloc(size * sizeof(int));
if (!marks) {
fprintf(stderr, "malloc failed\n");
exit(1);
}
for (i = 0; i < size; i++) {
printf("Enter element %d: ", i);
scanf("%d", &marks[i]);
}
printf("You entered: ");
for (i = 0; i < size; i++) {
printf("%d ", marks[i]);
}
free(marks);
puts("");
return 0;
}
size must have a defined value, for example:
#include <stdio.h>
int main()
{
int size;
size = 5; // size must be constant
int counter, marks[size];
for (counter = 0; counter < size; counter++)
{
scanf("%d", &marks[counter]);
}
//Printing it returns correct values:
for (counter = 0; counter < size; counter++)
{
printf("%d\n", marks[counter]);
}
}
You can instead input it's value from the user if you want.
However, if for some reason, size is to be defined after the array is declared, use pointers:
#include <stdio.h>
#include "stdlib.h"
int main()
{
int size;
int counter, *marks;
size = 5; //declared after the array
marks = (int *)malloc(size * sizeof(int));
for (counter = 0; counter < size; counter++)
{
scanf("%d", &marks[counter]);
}
//Printing it returns correct values:
for (counter = 0; counter < size; counter++)
{
printf("%d\n", marks[counter]);
}
//Don't forget to free the array in the end
free(marks);
}
I am trying to print the records after adding on to the original amount of records, and I am successful in doing so within the addRecords function, but outside of the function I have an error, but I am having understanding how. I'm passing the Names array through pointer and the classSize variable is global. So I don't see why it works in the addRecords function and not in the main funtion. All help is appreciated, thanks in advance.
#include <stdio.h>
#include <stdlib.h>
#define STRINGSIZE 21
int classSize;
void addRecords( char **Names);
int main() {
char **Names;
int i;
//User will be able to choose how many records he woudld like to input.
printf("Please indicate number of records you want to enter:\n");
scanf("%d", &classSize);
Names = malloc(classSize*sizeof(char*));
for (i = 0; i < classSize; i++) {
Names[i] = malloc(STRINGSIZE * sizeof(char));
}
printf("Please input records of students (enter a new line after each record), with following format: first name....\n");
for (i = 0; i < classSize; i++) {
scanf("%s", *(Names + i));
}
for (i = 0; i < classSize; i++) {
printf("%s ", *(Names+i));
printf("\n\n");
}
addRecords(Names);
printf("SECOND PRINT\n\n");
for (i = 0; i < classSize; i++) {
printf("%s \n", *(Names+i));
}
}
void addRecords(char **Names) {
int addition, i, temp;
temp = classSize;
printf("How many records would you like to add?\n");
scanf("%d", &addition);
classSize += addition;
Names = realloc(Names, (classSize) * sizeof(char*));
for (i = temp; i < (classSize); i++) {
Names[i] = malloc(STRINGSIZE * sizeof(char));
}
printf("Please input records of students (enter a new line after each record), with followingformat: first name....\n");
for (i=temp; i<classSize; i++) {
scanf("%s", *(Names +i));
}
printf("\n\n");
printf("FIRST PRINT\n\n");
for (i = 0; i < classSize; i++) {
printf("%s \n", *(Names+i));
}
printf("\n\n");
}
C uses pass-by-value. The Names inside addRecords is a different variable to Names inside main. A copy is created when you call the function.
To fix this you either need to pass Names by reference, or make it a global variable, or return the updated copy via function return value.
In your actual code, attempting to use Names in main() after it had been passed to realloc in the function, causes undefined behaviour (realloc makes its argument indeterminate).