I'm trying to compile a c code under linux using gcc-4.9 (tried also 5.4) while so, I faced a segmentation fault error.
Program received signal SIGSEGV, Segmentation fault.
0x080492e6 in dot (p1=0x8d9e6c0 <permy>, p2=0x3d77ca7c) at autrq.h:135
135 j = p2[i];
this is the part of code where the problem exists:
#define N 239
#define K 120
void dot(int p1[N], int p2[N]) {
int p3[N], i, j; //printf("\n debut dot ");
for (i = 0; i < N; i++){
p3[i] = p1[i];
}
for (i = 0; i < N; i++) {
j = p2[i];
if(j>=N){
printf("Too large\n");
}
else{
p1[i]=p3[j];
}
} //printf("\n fin dot ");
}
void GenAut(int permy[N]) {
int i, j, c, f;
//printf("\n debut GenAUT ");
int inf[K], mo[N], mi[N];
for (i = 0; i < N; i++){
permy[i] = i;
}
j = GenIdex(1, 100);
for (c = 0; c < j; c++) {
f = GenIdex(0, pos);
//printf("\n pos: %d et f %d ",pos,f);
dot(permy, automorf[f]);
}
}
automorf is an array n x n long (int automorf[n][n])
Can you please help correcting the problem?
Try this and see output
we have not p3[3]; and trying to access make error or undefined behavior.
#include <stdio.h>
#define N 3
void dot(int p1[N], int p2[N]) {
int p3[N], i, j; //printf("\n debut dot ");
for (i = 0; i < N; i++){
p3[i] = p1[i];
}
for (i = 0; i < N; i++) {
printf("i:%d p3[i]%d\n", i,p3[i]) ;
}
printf("\n") ;
for (i = 0; i < N; i++) {
j = p2[i];
printf("i:%d j:%d p3[%d]:%d\n", i, j, j, p3[j]) ;
p1[i]=p3[j];
}
//printf("\n fin dot ");
}
int
main(){
int x[N]={10,20,30};
int y[N]={1,2,3};
dot(x, y);
printf("\n");
return 0;
}
Related
My code never stops asking for input so I think I must've made an infinite loop, but I can't find where the error is. I've also noticed that when inserting the input line by line, it prints the result of one loop after inserting the first line of the second loop, which seems incorrect to me. Please help me debug. (For further context, the code is supposed to receive a number we'll call n, and then scan 3n more lines, which are basically n bundles of 3 similar lines. The 2nd and 3rd lines are two words with the same num of characters, and the 1st line is that num. The output is whether or not these words are anagrams.)
#include <stdio.h>
int main() {
int n, l;
scanf("%d\n", &n);
for (int i = 1; i <= n; i++) {
scanf("%d\n", &l);
char A[l], B[l];
for (int j = 0; j < l; j++) {
scanf("%c", &A[j]);
scanf("\n");
}
for (int j = 0; j < l; j++) {
scanf("%c", &B[j]);
scanf("\n");
}
for (int k = 0; k < l; k++) {
int result = 0;
for (int j = 0; j < l; j++) {
if (A[k] == B[j]) {
result = 1;
}
}
if (!result) {
printf("\nNO\n");
return 0;
}
}
printf("\nYES\n");
}
}
Example:
input:
2
6
listen
silent
4
Evil
live
output:
YES
NO
It's because you are asking for input over and over and over again,
Not sure what you are trying to achieve, but start by removing the extra scanfs
try this,
#include <stdio.h>
int main() {
int n, l;
scanf("%d\n", &n);
for (int i = 1; i <= n; i++) {
char A[l], B[l];
for (int k = 0; k < l; k++) {
int result = 0;
for (int j = 0; j < l; j++) {
if (A[k] == B[j]) {
result = 1;
}
}
if (!result) {
printf("\nNO\n");
return 0;
}
}
printf("\nYES\n");
}
}
Your scanf calls wait for an extra \n which requires more input to enter.
To fix this, remove the \n from your scanf calls. Also remove the extra calls when you enter A and B:
I have added some debug code to demonstrate where you are in your program execution while you enter your input.
#include <stdio.h>
int main() {
int n, l;
int res;
res=scanf("%d", &n);
printf ("res=%d, n=%d\n", res, n);
for (int i = 1; i <= n; i++) {
res = scanf("%d", &l);
printf ("res=%d, l=%d\n", res, l);
// char A[l], B[l];
char A[l+1], B[l+1];
for (int j = 0; j < l; j++) {
scanf(" %c", &A[j]);
}
printf ("A done\n");
for (int j = 0; j < l; j++) {
scanf(" %c", &B[j]);
}
printf ("B done\n");
A[l] = 0; B[l] = 0;
printf ("A=\"%s\" - B=\"%s\"\n", A, B);
...
Now your input should work properly.
But your code also contains another error.
You will treat "12344" and "11234" as correct match wchich is wrong.
To fix this you need to remove each matching character from B:
for (int k = 0; k < l; k++) {
int result = 0;
// We compare A[k] with the remaining characters in B only
for (int j = k; j < l; j++) {
if (A[k] == B[j]) {
result = 1;
B[j] = B[k]; // Replace matching character with non-matching character we checked earlier.
break;
}
}
if (!result) {
printf("\nNO\n");
return 0;
}
}
printf("\nYES\n");
This code stops as soon as the first match is found and removed that character from B.
The entries in B are rearranged to keep the unused entries at the end.
The full code looks like this:
#include <stdio.h>
int main() {
int n, l;
int res;
res=scanf("%d", &n);
printf ("res=%d, n=%d\n", res, n);
for (int i = 1; i <= n; i++) {
res = scanf("%d", &l);
printf ("res=%d, l=%d\n", res, l);
// char A[l], B[l];
char A[l+1], B[l+1];
for (int j = 0; j < l; j++) {
scanf(" %c", &A[j]);
}
printf ("A done\n");
for (int j = 0; j < l; j++) {
scanf(" %c", &B[j]);
}
printf ("B done\n");
A[l] = 0; B[l] = 0;
printf ("A=\"%s\" - B=\"%s\"\n", A, B);
for (int k = 0; k < l; k++) {
int result = 0;
for (int j = k; j < l; j++) {
if (A[k] == B[j]) {
result = 1;
B[j] = B[k];
break;
}
}
if (!result) {
printf("\nNO\n");
return 0;
}
}
printf("\nYES\n");
}
}
output:
~/stackoverflow$ ./test
4
res=1, n=4
2
res=1, l=2
12
A done
21
B done
A="12" - B="21"
YES
6
res=1, l=6
liver1
A done
evil1r
B done
A="liver1" - B="evil1r"
YES
3
res=1, l=3
111
A done
111
B done
A="111" - B="111"
YES
4
res=1, l=4
abcd
A done
dcbb
B done
A="abcd" - B="dcbb"
NO
I wrote a code that tries to multiply two matrices and put them in another result matrix. The code is working (I think) but it prints a very strange output .. I think it has to do with one of the functions pointing to something diffrent than the values, not sure though.
I tried checking each function in separete, also inizialzing each matrix with {0}.
#include <stdio.h>
#define SIZE 5
//#pragma warning(disable:4996)
//#define _CRT_SECURE_NO_WARNINGS
void read_mat(int mat[][SIZE])
{
int i, j, k = 0;
char s[100]; // assign input str to 's'
fgets(s,25,stdin); // recieving only the first 25 numbers
for (i = 0; i < SIZE; i++) {
for (j = 0; j < SIZE; j++) {
if (s[k] == '\0') { //if the string is just \0 -- the end of the string
mat[i][j] = 0;
}
else { // is there are values in s
if (s[k] != '0') { // binary matrix -- only 0 or 1
mat[i][j] = 1;
k++;
}
else {
mat[i][j] = 0;
++k;
}
}
}
}
}
void mult_mat(int mat_a[][SIZE], int mat_b[][SIZE], int result_mat[][SIZE])
{
int i, j, k;
for (i = 0; i < SIZE; i++) {
for (j = 0; j < SIZE; j++) {
for (k = 0; k < SIZE; k++) {
result_mat[i][j] += mat_a[i][k] * mat_b[k][j]; // by definition of matrix multiplication
k++;
}
}
}
}
void print_mat(int mat[][SIZE])
{
int i, j, k = 0;
for (i = 0; i < SIZE; i++) {
for (j = 0; j < SIZE; j++) {
printf("%3d", &(mat[i][j])); // printing each value with a 3*space
}
printf("\n");
}
}
int main()
{
int mat_a[SIZE][SIZE] = {0}, mat_b[SIZE][SIZE] = {0}, result_mat[SIZE][SIZE] = {0}; // initializing matricies to {0}
printf("Please Enter Values For Matrix 1\n");
read_mat(mat_a);
printf("Please Enter Values For Matrix 2\n");
read_mat(mat_b);
mult_mat(mat_a, mat_b, result_mat);
printf("The First Matrix Is :- \n");
print_mat(mat_a);
printf("The Second Matrix Is :- \n");
print_mat(mat_b);
printf("The Resultant Matrix Is :- \n");
print_mat(result_mat);
return 0;
}
the outout I am getting:
enter image description here
thanks!
improve your print function
void print_mat(int mat[][SIZE])
{
int i, j, k = 0;
for (i = 0; i < SIZE; i++) {
for (j = 0; j < SIZE; j++) {
printf("(%3d), ", &(mat[i][j])); // printing each value with a 3*space
}
printf("\n");
}
}
The title is pretty clear I think.
I am trying to create a program that calculates a 3x3 linear system using determinants, but I am getting a segmentation fault. Here is the code:
#include<stdio.h>
int determinant(int n, int m, int det[m][n])
{
int res;
res = det[0][0]*det[1][1] - det[0][1]*det[1][0];
return res;
}
int main(void)
{
int arr[3][4], det[2][2], i, j, D; //Dx1, Dx2, Dx3
for(i = 0; i < 3; i++)
{
printf("Eisagete tous suntelestes ths %dhs eksisoshs.", i+1);
scanf("%d %d %d %d", &arr[i][0], &arr[i][1], &arr[i][2], &arr[i][3]);
}
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; i++)
{
det[i][j] = arr[i+1][j+1];
}
}
D = arr[0][0]*determinant(2, 2, det);
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; i++)
{
det[i][j] = arr[i+1][j+((j == 1) ? 1 : 0)];
}
}
D -= arr[0][1]*determinant(2, 2, det);
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; i++)
{
det[i][j] = arr[i+1][j];
}
}
D += arr[0][2]*determinant(2, 2, det);
printf("%d\n", D);
}
I am getting the error right after completing the first for loop in main.
In the block:
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; i++)
{
det[i][j] = arr[i+1][j+1];
}
}
You increment i in both loops, and adding 1 more to it while reading from the array. So at arr[i+1] you are reading to far.
A segmentation fault basically means you are trying to read something you don't have access to.
You shoud never do what you're doing by passing static array sizes m and n as function argument:
int determinant(int n, int m, int det[m][n])
Check https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html for info
#include <stdio.h>
#include <pthread.h>
int arr[1000][1000];
int brr[1000][1000];
int h;
int f;
void *BMM(void *arg)
{
int* neo = (int*) arg;
int ne = *neo;
int sum = 0;
for(int i = 0; i < n; ++i)
{
sum += arr[x][i]*brr[x][f];
++f;
}
printf("%d\n", sum);
crr[x][h] = sum;
pthread_exit(NULL);
}
int main()
{
pthread_t* ar = malloc(3*sizeof(*ar));
printf("Enter the value of m and n\n");
scanf("%d %d",&m,&n);
for(int i = 0; i < m; ++i)
{
for(int j = 0; j < n; ++j)
{
scanf("%d",&arr[i][j]);
}
}
printf("Enter the value of p and q\n");
scanf("%d %d",&p,&q);
if(p != n)
{
printf("The matrix multiplication is not possible\n");
return 0;
}
int* id;
id = (int *)malloc(4*sizeof(int));
for(int i = 0; i < p; ++i)
{
for(int j = 0; j < q; ++j)
{
scanf("%d",&brr[i][j]);
}
}
for(x = 0; x < m; ++x)
{
for(z = 0; z < q; z+=4)
{
f = z;
h = z;
for(int k = 0; k < 3; ++k)
{
pthread_create(&ar[k],NULL,BMM,NULL);
}
for(int k = 0; k < 3; ++k)
{
pthread_join(ar[k],NULL);
}
}
}
for (int i = 0; i < m; ++i)
{
for(int j = 0; j < q; ++j)
{
printf("%d ",crr[i][j]);
}
printf("\n");
}
}
The above program is supposed to multiply two matrix by multiplying row one of matrix by all the columns of other matrix using 3 threads and then row two by all the other columns and so on and then store the respective values int another matrix but it is giving segmentation fault. Where am I going wrong?
I think your problem is here:
pthread_create(&ar[k],NULL,BMM,NULL);
^^^^
void *arg is NULL
and then:
void *BMM(void *arg)
{
int* neo = (int*) arg;
int ne = *neo; // Dereference NULL --> segmentation fault
Further this looks strange:
void *BMM(void *arg)
{
int* neo = (int*) arg;
int ne = *neo; // ne is never used !!
int sum = 0;
for(int i = 0; i < n; ++i) // Where does n come from ?
Perhaps it should be n instead of ne?
If n, x, f and h are global variables you are into trouble as all threads will work on the same variables. That would be real bad. Each thread needs it own variables.
BTW:
Always check the value returned by scanf - something like:
if (scanf("%d %d",&m,&n) != 2)
{
// Add error handling here
}
and
if (scanf("%d",&arr[i][j]) != 1)
{
// Add error handling here
}
I've been working on this for days but can't seem to make it work out.
Sorry in advance for the unholy length of this, so if anyone takes the time to go through it and try to understand this mess, I'd owe you.
Here is the code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
typedef struct cart {
int id;
char *nume;
} cart;
typedef struct pach {
int id, idCartier, strada, numar, prioritate, codificare;
float greutate;
char* mesaj;
int adresa[18];
} pach;
typedef struct post {
int id, nrPachete;
int vector[50];
} post;
int citeste(int *nrP, cart *cartier, pach *pachet, int *nrC) {
printf("Punctul 1\n");
int i, j;
scanf("%d", nrC);
for (i = 0; i < *nrC; i++) {
cartier[i].id = i;
char aux[500];
scanf("%s", aux);
cartier[i].nume = malloc(strlen(aux) + 1);
cartier[i].nume = aux;
printf("%d %s\n", cartier[i].id, cartier[i].nume);
}
scanf("%d", nrP);
for (i = 0; i < *nrP; i++) {
pachet[i].id = i;
char aux[500];
for (j = 0; j < 18; j++)
scanf("%d", &pachet[i].adresa[j]);
scanf("%d %f", &pachet[i].prioritate, &pachet[i].greutate);
getchar();
fgets(aux, 256, stdin);
pachet[i].mesaj = malloc(strlen(aux) + 1);
pachet[i].mesaj = aux;
printf("%d\n", pachet[i].id);
for (j = 0; j < 18; j++)
printf("%d ", pachet[i].adresa[j]);
printf("\n%d %.6f ", pachet[i].prioritate, pachet[i].greutate);
printf("%s", pachet[i].mesaj);
}
return *nrP;
}
void extrage(int *nrP, pach *pachet) {
printf("\nPunctul 2\n");
int i, j;
for (i = 0; i < *nrP; i++) {
pachet[i].idCartier = 0;
pachet[i].strada = 0;
pachet[i].numar = 0;
for (j = 0; j < 5; j++)
pachet[i].idCartier += pachet[i].adresa[j] * pow(2, (4 - j));
for (j = 5; j < 10; j++)
pachet[i].strada += pachet[i].adresa[j] * pow(2, (9 - j));
for (j = 10; j < 18; j++)
pachet[i].numar += pachet[i].adresa[j] * pow(2, (17 - j));
printf("%d %d ", pachet[i].id, pachet[i].idCartier);
printf("%d %d\n", pachet[i].strada, pachet[i].numar);
}
}
void distribuie(int *nrP, pach *pachet, post *postas, int *nrC, cart *cartier) {
printf("Punctul 3\n");
int i, j;
for (i = 0; i < *nrC; i++) { // FOR-1A
postas[i].nrPachete = 0;
postas[i].id = i;
for (j = 0; j < 50; j++)
postas[i].vector[j] = 0;
}
for (i = 0; i < *nrC; i++) { // FOR-1B
for (j = 0; j < *nrP; j++) {
if (cartier[i].id == pachet[j].idCartier) {
postas[i].vector[postas[i].nrPachete] = pachet[j].id;
postas[i].nrPachete++;
}
}
printf("%d %d ", postas[i].id, postas[i].nrPachete);
for (j = 0; j < postas[i].nrPachete; j++)
printf("%d ", postas[i].vector[j]);
printf("\n");
}
}
void ordoneaza(pach *pachet, int *nrC, post *postas) {
printf("Punctul 4\n");
pach aux;
int i, j, k = 0, schimbat = 1;
for (i = 0; i < *nrC; i++) {
while (schimbat) {
schimbat = 0;
for (j = 0; j < postas[i].nrPachete - k; j++)
if (pachet[postas[i].vector[j]].prioritate < pachet[postas[i].vector[j+1]].prioritate) {
aux = pachet[postas[i].vector[j]];
pachet[postas[i].vector[j]] = pachet[postas[i].vector[j+1]];
pachet[postas[i].vector[j+1]] = aux;
schimbat = 1;
}
k++;
}
k = 0;
schimbat = 1;
for (j = 0; j < postas[i].nrPachete; j++) {
for (k = j; k < postas[i].nrPachete; k++) {
if (pachet[postas[i].vector[j]].prioritate == pachet[postas[i].vector[k]].prioritate)
if (pachet[postas[i].vector[j]].greutate < pachet[postas[i].vector[k]].greutate) {
aux = pachet[postas[i].vector[j]];
pachet[postas[i].vector[j]] = pachet[postas[i].vector[k]];
pachet[postas[i].vector[k]] = aux;
}
}
}
}
for (i = 0; i < *nrC; i++)
for (j = 0; j < postas[i].nrPachete; j++) {
postas[i].vector[j] = pachet[postas[i].vector[j]].id;
}
for (i = 0; i < *nrC; i++) {
printf("%d %d ", postas[i].id, postas[i].nrPachete);
for (j = 0; j < postas[i].nrPachete; j++)
printf("%d ", postas[i].vector[j]);
printf("\n");
}
}
int main() {
int nrP, nrC;
pach pachet[1600];
post postas[32];
cart cartier[32];
citeste(&nrP, &cartier[32], &pachet[1600], &nrC);
extrage(&nrP, &pachet[1600]);
distribuie(&nrP, &pachet[1600], &postas[32], &nrC, &cartier[32]);
ordoneaza(&pachet[1600], &nrC, &postas[32]);
return (0);
}
Short info on what the program does:
The citeste function should read the cartier and pachet structures. All of them. And then print those in a bit different format.
The extrage function should take every pachet, and use the adresa (written in BINARY) to convert its 3 parts and obtain the strada, numar and idCartier. Then also print those.
Distribuie checks if the pachet is distributed to a postas (distributed means pachet.idCartier == postas.id), if not it distributes it.
Ordoneaza takes every postas's vector and sorts it after the prioritate (or greutate if the prioritate-s are equal).
But it doesn't work as intended and also gives weird Segmentation Faults.
For example if I comment out the distribuie function, it gives me segfault right after extrage. If I put it back, it gives segfault right after doing it. And if I uncomment everything, it gives segfault at the end again.
If anyone actually read all of this and would be willing to reply, I'd highly appreciate it. Any bit of advice helps!
I did not read your code, but your title said you had trouble passing array of structures. I am attaching a working snippet hope it will help you get around your problem.
#include<stdio.h>
typedef struct employee{
int empId;
char name[10];
}EMP;
void arrayOfStruct(EMP *a, int size)
{
printf("%d\t%d",a[0].empId,a[3].empId);
}
int main()
{
EMP NC[4];
NC[0].empId = 9;
NC[3].empId = 2;
arrayOfStruct(&NC[0],sizeof(NC)/sizeof(NC[0]));
}
with the help of size you can never go beyond the memory allocated for structures.
In case you, want to pass higher dimensional arrays, you have to hard code all the size of arrays except the outer most.
void arrayOfStruct(EMP a[][4], int size)
{
// to do
}
int main()
{
EMP NC[2][4];
...
arrayOfStruct(NC,sizeof(NC)/sizeof(NC[0]));
}
as you see, I did not specify the higher most size of array, which I am passing via other arguement.
Why do I need to specify size of inner dimensions ?
Lets take an example, for suppose you have int[4][4], and you are trying to pass array to a function via int[3][], how does a compiler know how many inner blocks to create, in other case via int[][3], the compiler can easily understand that it has to make inner block of size 3 for each outer array.