I try to read a text file and pass all integers to a 2 dimensional array one by one. But when i print what I tried to pass, I get weird outputs. What could be the problem?
For example if the text is:
0 1 1 1 0 1 1 0 1 1 1 1
I get this:
index=-2 index=1967626458 index=1967694074 index=207568 index=207320 index=2686776 index=1967693597 index=0 index=0 index=2686832 index=236 index=228 index=3
Here is the code:
#include<stdio.h>
int main()
{
FILE *input;
//read file!
if((input = fopen("abc.txt","r"))==NULL){
printf("Error in reading file !\n");
return 0;
}
int C = 4;
int R = 3;
int M[3][4];
int x=0;
int y=0;
int c;
//array of sorted list!
while(!feof(input)){
if(!feof(input)){
fscanf( input, "%d",&c);
M[x][y]=c;
y++;
if(y==C){
x++;
y=0;
}
printf("index=%d \n",M[x][y]);
}
}
system("pause");
}
The printout is wrong because you're changing the values of x and y between when you set the variable and when you try to print it. You need to move the printf() before the part where you increment x and y, but after you assign to the array.
As it stands right now, you assign to the array, then print the next, as yet unassigned, value. It's whatever value happens to be in that memory, such as -2 or 1967626458.
just increment you y variable after printing index.
#include<stdio.h>
int main()
{
FILE *input;
//read file!
if((input = fopen("abcd.txt","r"))==NULL)
{
printf("Error in reading file !\n");
return 0;
}
int C = 4;
int R = 3;
int M[3][4];
int x=0;
int y=0;
int c;
//array of sorted list!
while(!feof(input))
{
if(!feof(input))
{
fscanf( input, "%d",&c);
M[x][y]=c;
//y++ ; not increment here
if(y==C)
{
x++;
y=0;
}
printf("index=%d \n",M[x][y]);
y++;//increment here
}
}
system("pause");
}
Related
enter image description here
Sorry im new to coding . I have searched up possible solutions for this on here but they didnt work. Im also confused on why some code appears grey compared to the rest.
https://1drv.ms/w/s!Ag8vVFKVPyOg6HeYLehGjQKdvl_3?e=QHY6t9
#include <stdio.h>
// initialised variables
int i = 0;
int count = 0;
void displayfunction(void);
int month = 0;
void highervalues(float array1[12], float array2[12]);
void highervalues(float array1[12], float array2[12]) {
for (i = 12; i > 0; i--) {
if (array2[i] > array1[i]) {
count = count + 1;
}
}
}
//Reading values for array1 and array2
void displayfunction(void) {
highervalues(array1[12] , array2[12]);
for (i = 0; i < 12; i++)
{
month = month + 1; // month increases by 1 after each input
printf_s("enter values for year 1 month %d", month);
scanf_s("%f", &array1[i]);
}
for (month = 12; month > 0; month--) {
}
for (i = 0; i < 12; i++) {
month = month + 1;
printf_s("enter values for year 2 month %d", month);
scanf_s("%f", &array2[i]);
}
}
/*comapring 2 arrays and increasing count value if there are any value in array2
are greater than array1*/
int main() {
displayfunction();
int array1[12];
int array2[12];
}
You have a fundamental misunderstanding of variable scope
int main() {
displayfunction();
int array1[12];
int array2[12];
}
Those arrays are only available in main. If you want other functions to operate on them you have to pass them as paramters to those functions. Plus they dont exist at the point where you try to call displayFunction
So change
void displayfunction(void)
to
void displayfunction(float array1[12], float array2[12])
then in main do
int main() {
int a1[12];
int a2[12];
displayfunction(a1, a2);
}
Note that I have changed the names here just to emphasise that its the not the fact that the names are the same thats important.
Basically the code here takes some string and gives a string wihtout special character .
But when I give input, the Output gives the desired output. But it gives me infinite output.
What I want is user will give infinite input and will get desired output .
int main()
{
int g= 2; char C;
while (1) {
char s[257];
scanf("%[^\n]", s);
int i;
int j= strlen (s);
for (i=0; i< j; i++){
if( (s[i]>='a'&& s[i]<='z')|| (s[i]>='A' && s[i]<='Z') || (s[i]==' ') )
printf ("%c",s[i]);
}
}
return 0;
}
I have read other threads on pset5 Valgrind memory errors, but that didn't help me. I get 0 leaks, but this instead:
==1917== Conditional jump or move depends on uninitialised value(s)
Looks like you're trying to use a variable that might not have a value? Take a closer look at line 34 of dictionary.c.
The error refers to line 34 which is this: lower[i] = tolower(word[i]);
To supply context, the code below attempts to check if a word exists in the dictionary that has been uploaded to a hash table. I am attempting to convert the wanted word to lowercase because all the dictionary words are also lowercase and so that their hashes would be identical. The program successfully completes all tasks, but then stumbles upon these memory errors.
Any hints as to why Valgrind is mad at me? Thank you!
// Returns true if word is in dictionary else false
bool check(const char *word)
{
char lower[LENGTH + 1];
//Converts word to lower so the hashes of the dictionary entry and searched word would match
for (int i = 0; i < LENGTH + 1; i++)
{
lower[i] = tolower(word[i]);
}
// Creates node from the given bucket
node *tmp = table[hash(lower)];
// Traverses the linked list
while (tmp != NULL)
{
if (strcasecmp(word, tmp->word) == 0)
{
return true;
}
tmp = tmp->next;
}
return false;
}
Below is the whole dictionary.c file:
// Implements a dictionary's functionality
#include <string.h>
#include <strings.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include "dictionary.h"
// Represents a node in a hash table
typedef struct node
{
char word[LENGTH + 1];
struct node *next;
}
node;
// Number of buckets in hash table 26^3
const unsigned int N = 17576;
// Hash table
node *table[N];
int count = 0;
// Returns true if word is in dictionary else false
bool check(const char *word)
{
char lower[LENGTH + 1];
//Converts word to lower so the hashes of the dictionary entry and searched word would match
for (int i = 0; i < LENGTH + 1; i++)
{
lower[i] = tolower(word[i]);
}
// Creates node from the given bucket
node *tmp = table[hash(lower)];
// Traverses the linked list
while (tmp != NULL)
{
if (strcasecmp(word, tmp->word) == 0)
{
return true;
}
tmp = tmp->next;
}
return false;
}
// Hashes word to a number
unsigned int hash(const char *word)
{
// Modified hash function by Dan Berstein taken from http://www.cse.yorku.ca/~oz/hash.html
unsigned int hash = 5381;
int c;
while ((c = *word++))
{
hash = (((hash << 5) + hash) + c) % N; /* hash * 33 + c */
}
return hash;
}
// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)
{
FILE *inptr = fopen(dictionary, "r");
if (dictionary == NULL)
{
printf("Could not load %s\n.", dictionary);
return false;
}
// Create a char array to temporarily hold the new word (r stands for read)
char r_word[N+1];
// Until the end of file
while (fscanf(inptr, "%s", r_word) != EOF)
{
// Increments count
count++;
// Create a node
node *new_node = malloc(sizeof(node));
if (new_node == NULL)
{
unload();
return false;
}
strcpy(new_node->word, r_word);
// Hash the node
int index = hash(new_node->word);
// Places the node at the right index
new_node->next = table[index];
table[index] = new_node;
}
fclose(inptr);
return true;
}
// Returns number of words in dictionary if loaded else 0 if not yet loaded
unsigned int size(void)
{
if (&load == false)
{
return '0';
}
else
{
return count;
}
}
// Unloads dictionary from memory, returning true if successful else false
bool unload(void)
{
// Interates over the array
for (int i = 0; i < N; i++)
{
node *head = table[i];
while (head != NULL)
{
node *tmp = head;
head = head->next;
free(tmp);
}
}
return true;
}
This loop iterates through the maximum length of word-
for (int i = 0; i < LENGTH + 1; i++)
{
lower[i] = tolower(word[i]);
}
Except if you look at how word is created-
while (fscanf(inptr, "%s", r_word) != EOF)
{
// Increments count
count++;
// Create a node
node *new_node = malloc(sizeof(node));
if (new_node == NULL)
{
unload();
return false;
}
strcpy(new_node->word, r_word);
Notice, the variable r_word, may not be exactly of length LENGTH + 1. So what you really have in word is N number of characters, where N is not necessarily LENGTH + 1, it could be less.
So looping over the entire 0 -> LENGTH + 1 becomes problematic for words that are shorter than LENGTH + 1. You're going over array slots that do not have a value, they have garbage values.
What's the solution? This is precisely why c strings have \0-
for (int i = 0; word[i] != '\0'; i++)
{
lower[i] = tolower(word[i]);
}
This will stop the loop as soon as the NULL character is reached, which, you must have already learnt, marks the end of a string - aka a char array.
There may still be more errors in your code. But for your particular question - reading out of bounds is the answer.
I am currently conducting empirical studies to evaluate the run-time complexities of the quicksort, and mergesort algorithms. To do this I run a random number generator that stores whatever amount of numbers I specify in a binary file. The ranges of those numbers are from 1-1,000,000.I then run tests of each algorithm starting from 100,000 numbers, incrementing by 50,000 each time, until 1,000,000 numbers are sorted on the last run. So 20 tests each. I have successfully completed each algorithm but my results are kind of puzzingly. This is a graph showing my results.
I understand that quicksort has a worst case of O(n2) time, but typically O(n·lg(n)) time. Mergesort has Θ(n·lg(n)) time.
Also I would like to note that when I started the timer I just used clock() from time.h, and calculated the time elapsed. I started my timer one line of code before I called my sorting function.
What I dont understand is how my graph shows mergesort is always double the time, and reaching triple the time to sort numbers compared to quicksort.
My only thought is that for my mergesort algorithm every time I divide my array in half I use malloc to create a new integer array for each half. Of course this means a large amount of calls are made to malloc considering the number sizes I am sorting.
int* mergeSort(int* nums, int size){
int* left;
int* right;
int middle = size/2;
if(size <= 1)
return nums;
split(nums, size, &left, &right, middle);
//I dont understand why the code below wouldnt work in place of the split()
//when i run it, in main, nothing gets printed out. I guess i lose my pointer to the beginning of my array.
//left = nums;
//right = nums+middle;
left = mergeSort(left, middle);
right = mergeSort(right, size - middle);
merge(nums,left,right,middle,size - middle);
free(left);
free(right);
return nums;
}
void split(int* nums, int size, int** left, int** right, int middle){
int *lft = (int*) malloc ((sizeof(int) * middle));
int *rght = (int*) malloc ((sizeof(int) * size - middle));
int mid = middle;
int upMid = size - middle;
int i;
for(i=0; i < mid; i++)
lft[i] = nums[i];
for(i=0; i < upMid; i++)
rght[i] = nums[i+middle];
*left = lft;
*right = rght;
}
void merge(int* num, int* left, int* right, int sizeLeft, int sizeRight){
int i,j,k,n;
i=j=k=0;
n=sizeLeft + sizeRight;
while(k < n){
if(i< sizeLeft){
if(j<sizeRight){
insert(num,left,right,&i,&j,&k);
}
else{
append(num, left, sizeLeft, &i, &k);
}
}
else{
append(num,right,sizeRight,&j,&k);
}
}
}
void insert(int* num, int* left, int* right, int* i, int* j, int* k){
/*int i,j,k,n;*/
if(left[*i]<right[*j]){
num[*k] = left[*i];
(*i)++;
}
else{
num[*k] = right[*j];
(*j)++;
}
(*k)++;
}
void append(int* num, int* half, int sizeHalf, int* i, int* k){
while(*i < sizeHalf){
num[*k]= half[*i];
(*i)++; (*k)++;
}
}
I would greatly appreciate any feedback on this question of mine, and any advice on maybe making my mergesort function more efficient. Thanks!!
I have implemented a merge sort algorithm, you can have a look. I malloc a bak array at the beginning of mergeSort and every merge use the it afterwards.
#include <string>
#include <stdlib.h>
void _mergeSort(int *array, int *bakArray, int len) ;
void mergeSort(int *array, int len)
{
int *bak = (int *)malloc(sizeof(int)*len) ;
_mergeSort(array, bak, len) ;
free(bak) ;
}
void _mergeSort(int *array, int *bakArray, int len)
{
if (len >= 2) {
int leftLen = len/2 ;
_mergeSort(array, bakArray, leftLen) ;
_mergeSort(array+leftLen, bakArray, len-leftLen) ;
int *pa = array ;
int *pb = array+leftLen ;
int aIndex = 0 ;
int bIndex = 0 ;
while (aIndex < leftLen && bIndex < len-leftLen) {
int a = pa[aIndex] ;
int b = pb[bIndex] ;
if (a < b) {
bakArray[aIndex+bIndex] = a ;
++aIndex ;
} else if (a == b) {
bakArray[aIndex+bIndex] = a ;
bakArray[aIndex+bIndex+1] = a ;
++aIndex ;
++bIndex ;
} else {
bakArray[aIndex+bIndex] = b ;
++bIndex ;
}
}
if (aIndex < leftLen) {
memcpy(bakArray+aIndex+bIndex, pa+aIndex, sizeof(int)*(leftLen-aIndex)) ;
} else if (bIndex < len-leftLen) {
memcpy(bakArray+aIndex+bIndex, pb+bIndex, sizeof(int)*(len-leftLen-bIndex)) ;
}
memcpy(array, bakArray, sizeof(int)*len) ;
}
}
static const int MaxArraySize = 100 ;
int main()
{
srand(time(NULL)) ;
int array[MaxArraySize] ;
for (int i = 0 ; i < MaxArraySize; ++i) {
array[i] = rand() % 10000 ;
}
mergeSort(array, MaxArraySize) ;
for (int i = 0 ; i < MaxArraySize; ++i) {
printf("%d ", array[i]) ;
}
printf("\n") ;
return 0 ;
}
while doing a program related to variable argument function i
got the header file stdarg.h and have done some simple problem using it
but now when i a changing the actual argument's type it is showing some weird behaviour
here is my code:
#include<stdio.h>
#include<stdarg.h>
void fun(int a,...)
{
va_list k;
va_start(k,a);
int i=0;
printf("%d ",a);
while((i=va_arg(k,int)!=0)
{
printf(" %d ",i);
}
va_end(k);
}
int main()
{
fun(1,2,3,4,5,6);
printf("\n");
fflush(); //and without flush it is also showing some extra garbage value
fun(2,4,5);
printf("\n");
fflush();
fun('c','f','g','l');
return 0;
}
If you use the integer value 0 to indicate end of the argument list, you should also pass a 0 to fun.
fun(1,2,3,4,5,6,0);
fun(2,4,5,0);
First, end your list with 0, because you check for !=0 to detect the end. And also:
while((i=va_arg(k,int))!=0)
instead of
while(i=va_arg(k,int)!=0)
!= has higher precedence than =
This will give you the expected output:
1 2 3 4 5 6
Here's the complete code:
#include<stdio.h>
#include<stdarg.h>
void fun(int a,...)
{
va_list k;
va_start(k,a);
int i=0;
printf("%d ",a);
while((i=va_arg(k,int))!=0)
{
printf(" %d ",i);
}
va_end(k);
}
int main()
{
fun(1,2,3,4,5,6,0);
printf("\n");
//fun(2,4,5,0);
printf("\n");
//fun('c','f','g','l','\0');
getch();
return 0;
}