I am doing the CS50 course and am on week 2. One of the problems of week 2 is called "Caesar". Essentially you have to write code which cyphers text by shifting letters that use the users inputted preferred number. After running my code I keep getting this error
"error: implicitly declaring library function 'strlen' with
type 'unsigned long (const char *)'
[-Werror,-Wimplicit-function-declaration]
for(i = 0, l = strlen(text); i < n; i++)"
This is the code:
int main(int argc, string argv[])
{
string n = argv[1];
int y = argc;
int key = get_int("./caesar ");//getting the number from the user
int k = (key);//assigning key a variable name.
string text = get_string("plaintext: ");//letting the user input their text.
if (key < 1)//Trying to make limit for acceptable input.
{
printf("ERROR");
return 1;
}
int l;
int i;
//for loop containing the encipher process
for(i = 0, l = strlen(text); i < n; i++)
{
if(isalpha(i))
{
if (isupper[i])
{
printf("ciphertext: %c",(text[i] + k)%26 + 65);
}
else (islower[i])
{
printf("ciphertext: %c",(text[i] + k)%26 + 65);
}
}
}
printf("ciphertext: %c", d || c);
return;
int checking_key(int y,string n)
int num = argc;
string key = y;
int num_key = atoi(key);
if(argc != 2)
{
return 0;
}
else
{
if (num_key > 0)
{
return num_key;
}
else
{
return 0;
}
}
}
From man strlen:
Synopsis
#include <string.h>
size_t strlen(const char *s);
Just like one needs to "include" cs50.h to use any of the get_* functions, string.h must be "include"d to access its functions, eg strlen.
Additionally (per comments):
The "ordered comparison" in the compile error
ordered comparison between pointer and integer ('int' and 'string' (aka 'char *')) [-Werror] for(i = 0, l = strlen(text); i < n; i++)
is i < n. Error says one of them is an int and one of them is a string.
On closer inspection this program is a long way from a clean compile. Recommend you follow along with the spec and "approach this problem one step at a time"
Related
I just want to know that for finding the Krishnamurthy number, we have to first find the factorial of the digits, then the addition of those numbers. (like, 1!+4!+5! = 145).
So, below is my code, and I have applied a factorial function over there. But the output is not coming in favor (145 is not a Kri...).
#include <stdio.h>
#include <stdlib.h>
void main()
{
int digit,factorial = 1, temp, input, sum = 0;
printf("Enter a Number:\n");
scanf("%d",&input);
int Factorial(int digit){
factorial = factorial*digit;
return 0;
}
temp = input;
while(temp>0){
digit = temp%10;
temp = temp/10;
sum = sum + Factorial(digit);
}
if(sum==input){
printf("%d is a Krishnamurthy Number",input);
}
else{
printf("%d is not a Krishnamurthy Number",input);
}
}
Have I done anything wrong in logic, or function declaration or definition? Please help.
your factorial function is not performing correctly. factorial means, multiplication of all digits starting from n downto 1 -
(n-1) * (n-2) * ... * (n)
but your function is not giving the desired result you want.
int Factorial(int digit){
factorial = factorial*digit;
return 0;
}
you need to change that function to get the factorial value of a number, you can either iterate a loop downto one or use a recursive approach to get the factorial.
int Factorial(int digit){
int result = 1;
for(int i=n; i>=1; i--){
result *= i;
}
return result;
}
or
int Factorial(int digit) {
if(n <= 1) return digit;
return digit * Factorial(digit-1);
}
you can follow the thread to understand the depth of recursive function mentioned above.
#include<stdio.h>
int main(int argc, char* argv[], char* envp[])
{
int sum = 0,
int a,
int p = 0,
int d,
int i,
int fact;
//code
printf("Enter a number: ");
scanf("%d", &a);
p = a;
while (a > 0)
{
fact = 1;
d = a % 10;
a /= 10;
for (i = d; i >= 1; i--)
{
fact *= i;
}
sum += fact;
}
if (sum == p)
printf("It is a Krishnamurthy number.\n");
else
printf("It is not a Krishnamurthy number.\n");
printf("\n\n");
return(0);
}
This program checks distinctness in an array. (no repeated values in an array I.e if 1 2 3 3 4 is an array it is not distinct). this code Won't compile although (I believe that) index of array did not go out of range in for loop.
theRun-Time Check Failure says stack around variable 'n' was corrupted when I enter n =12. BUT says stack around variable 'A' was corrupted when I enter n = 10. with exactly the same variables entered in the array in the second step. (the error shows up after entering the fourth integer)
#include <iostream>
using namespace std;
int main()
{
int n;
int A[] = {0};
int integer;
cout<<"Enter the size of the array\n";
cin>>n;
cout<<"enter "<<n<<" integers\n";
for (int i = 0 ; i < n ; i++)
{
cin>>A[i];
}
for (int i = 0 ; i < n ; i++)
{
for (int j = 0 ; j < n - i; j++)
{
if(A[j+1] > A[j])
{
int temp;
temp = A[j];
A[j+1] = A[j];
A[j+1] = temp;
}
}
}
for (int i = 0 ; i < n; i++)
{
if (A[i] - A[i+1] ==0 ){
cout<<"\nThe Array Is Not Distinct !\n";
break;
}
else
{
cout<<"\nThe Array Is Distinct !\n";
}
}
system("pause");
return 0;
}
My doubts are as follows :
1 : how to send 'str' from function 'fun' , So that i can display it in main function.
2 : And is the return type correct in the code ?
2 : the current code is displaying some different output.
char * fun(int *arr)
{
char *str[5];
int i;
for(i=0;i<5;i++)
{
char c[sizeof(int)] ;
sprintf(c,"%d",arr[i]);
str[i] = malloc(sizeof(c));
strcpy(str[i],c);
}
return str;
}
int main()
{
int arr[] = {2,1,3,4,5},i;
char *str = fun(arr);
for(i=0;i<5;i++)
{
printf("%c",str[i]);
}
return 0;
}
how to send 'str' from function 'fun' , So that i can display it in main function.
This is the way:
char* str = malloc( size );
if( str == NULL ) {
fprintf( stderr,"Failed to malloc\n");
}
/* Do stuff with str, use str[index],
* remember to free it in main*/
free(str);
And is the return type correct in the code ?
No, Probably char** is the one you need to return.
the current code is displaying some different output.
Consider explaining what/why do you want to do ? The way you have written, seems completely messed up way to me. You're passing array of integer but not its length. How is the fun() supposed to know length of array? Another problem is array of pointers in fun().
You can't write a int to a char (See the both size). So I used char array instead.
However, I'm not sure if this is what you want to do (might be a quick and dirty way of doing it):
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char**
fun(int *arr, int size)
{
char **str = malloc( sizeof(char*)*size );
if( str == NULL ) {
fprintf( stderr, "Failed malloc\n");
}
int i;
for(i=0;i<5;i++) {
str[i] = malloc(sizeof(int));
if( str == NULL ) {
fprintf( stderr, "Failed malloc\n");
}
sprintf(str[i],"%d",arr[i]);
}
return str;
}
int
main()
{
int arr[] = {2,1,3,4,5},i;
char **str = fun(arr, 5);
for(i=0;i<5;i++) {
printf("%s\n",str[i]);
free(str[i]);
}
free(str);
return 0;
}
I made these changes to your code to get it working:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char **fun(int *arr)
{
char **str = malloc(sizeof(char *) * 5);
int i;
for(i = 0; i < 5; i++) {
if ((arr[i] >= 0) && (arr[i] <= 9)) {
char c[2] ;
sprintf(c, "%d", arr[i]);
str[i] = (char *) malloc(strlen(c) + 1);
strcpy(str[i],c);
}
}
return str;
}
int main()
{
int arr[] = {2, 1, 3, 4, 5}, i;
char **str = fun(arr);
for(i = 0; i < 5; i++) {
printf("%s", str[i]);
free(str[i]);
}
printf("\n");
free(str);
return 0;
}
Output
21345
I added a check to make sure that arr[i] is a single digit number. Also, returning a pointer to a stack variable will result in undefined behavior, so I changed the code to allocate an array of strings. I don't check the return value of the malloc calls, which means this program could crash due to a NULL pointer reference.
This solution differs from the others in that it attempts to answer your question based on the intended use.
how to send 'str' from function 'fun' , So that i can display it in main function.
First, you need to define a function that returns a pointer to array.
char (*fun(int arr[]))[]
Allocating variable length strings doesn't buy you anything. The longest string you'll need for 64bit unsigned int is 20 digits. All you need is to allocate an array of 5 elements of 2 characters long each. You may adjust the length to suit your need. This sample assumes 1 digit and 1 null character. Note the allocation is done only once. You may choose to use the length of 21 (20 digits and 1 null).
For readability on which values here are related to the number of digits including the terminator, I'll define a macro that you can modify to suit your needs.
#define NUM_OF_DIGITS 3
You can then use this macro in the whole code.
char (*str)[NUM_OF_DIGITS] = malloc(5 * NUM_OF_DIGITS);
Finally the receiving variable in main() can be declared and assigned the returned array.
char (*str)[NUM_OF_DIGITS] = fun(arr);
Your complete code should look like this:
Code
char (*fun(int arr[]))[]
{
char (*str)[NUM_OF_DIGITS] = malloc(5 * NUM_OF_DIGITS);
int i;
for(i=0;i<5;i++)
{
snprintf(str[i],NUM_OF_DIGITS,"%d",arr[i]); //control and limit to single digit + null
}
return str;
}
int main()
{
int arr[] = {24,1,33,4,5},i;
char (*str)[NUM_OF_DIGITS] = fun(arr);
for(i=0;i<5;i++)
{
printf("%s",str[i]);
}
free(str);
return 0;
}
Output
2413345
With this method you only need to free the allocated memory once.
I am working on the Vigenere exercise from Harvard's CS50 (in case you noticed I'm using string and not str).
My program gives me a Floating Point Exception error when I use "a" in the keyword.
It actually gives me that error
when I use "a" by itself, and
when I use "a" within a bigger word it just gives me wrong output.
For any other kind of keyword, the program works perfectly fine.
I've run a million tests. Why is it doing this? I can't see where I'm dividing or % by 0. The length of the keyword is always at least 1. It is probably going to be some super simple mistake, but I've been at this for about 10 hours and I can barely remember my name.
#include <stdio.h>
#include <cs50.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
int main (int argc, string argv[])
{
//Error message if argc is not 2 and argv[1] is not alphabetical
if (argc != 2)
{
printf("Insert './vigenere' followed by an all alphabetical key\n");
return 1;
}
else if (argv[1])
{
for (int i = 0, n = strlen(argv[1]); i < n; i++)
{
if (isalpha((argv[1])[i]) == false)
{
printf("Insert './vigenere' followed by an all alphabetical key\n");
return 1;
}
}
//Store keyword in variable
string keyword = argv[1];
//Convert all capital chars in keyword to lowercase values, then converts them to alphabetical corresponding number
for (int i = 0, n = strlen(keyword); i < n; i++)
{
if (isupper(keyword[i])) {
keyword[i] += 32;
}
keyword[i] -= 97;
}
//Ask for users message
string message = GetString();
int counter = 0;
int keywordLength = strlen(keyword);
//Iterate through each of the message's chars
for (int i = 0, n = strlen(message); i < n; i++)
{
//Check if ith char is a letter
if (isalpha(message[i])) {
int index = counter % keywordLength;
if (isupper(message[i])) {
char letter = (((message[i] - 65) + (keyword[index])) % 26) + 65;
printf("%c", letter);
counter++;
} else if (islower(message[i])) {
char letter = (((message[i] - 97) + (keyword[index])) % 26) + 97;
printf("%c", letter);
counter++;
}
} else {
//Prints non alphabetic characters
printf("%c", message[i]);
}
}
printf("\n");
return 0;
}
}
This behavior is caused by the line keyword[i] -= 97;, there you make every 'a' in the key stream a zero. Later you use strlen() on the transformed key. So when the key starts with an 'a', keywordLength therefor is set to zero, and the modulo keywordLength operation get into a division by zero. You can fix this by calculating the keyword length before the key transformation.
I am new to c++ programming I have to call a function with following arguments.
int Start (int argc, char **argv).
When I try to call the above function with the code below I get run time exceptions. Can some one help me out in resolving the above problem.
char * filename=NULL;
char **Argument1=NULL;
int Argument=0;
int j = 0;
int k = 0;
int i=0;
int Arg()
{
filename = "Globuss -dc bird.jpg\0";
for(i=0;filename[i]!=NULL;i++)
{
if ((const char *)filename[i]!=" ")
{
Argument1[j][k++] = NULL; // Here I get An unhandled
// exception of type
//'System.NullReferenceException'
// occurred
j++;
k=0;
}
else
{
(const char )Argument1[j][k] = filename [j]; // Here I also i get exception
k++;
Argument++;
}
}
Argument ++;
return 0;
}
Start (Argument,Argument1);
Two things:
char **Argument1=NULL;
This is pointer to pointer, You need to allocate it with some space in memory.
*Argument1 = new char[10];
for(i=0, i<10; ++i) Argument[i] = new char();
Don't forget to delete in the same style.
You appear to have no allocated any memory to you arrays, you just have a NULL pointer
char * filename=NULL;
char **Argument1=NULL;
int Argument=0;
int j = 0;
int k = 0;
int i=0;
int Arg()
{
filename = "Globuss -dc bird.jpg\0";
//I dont' know why you have 2D here, you are going to need to allocate
//sizes for both parts of the 2D array
**Argument1 = new char *[TotalFileNames];
for(int x = 0; x < TotalFileNames; x++)
Argument1[x] = new char[SIZE_OF_WHAT_YOU_NEED];
for(i=0;filename[i]!=NULL;i++)
{
if ((const char *)filename[i]!=" ")
{
Argument1[j][k++] = NULL; // Here I get An unhandled
// exception of type
//'System.NullReferenceException'
// occurred
j++;
k=0;
}
else
{
(const char )Argument1[j][k] = filename [j]; // Here I also i get exception
k++;
Argument++;
}
}
Argument ++;
return 0;
}
The first thing you have to do is to find the number of the strings you will have. Thats easy done with something like:
int len = strlen(filename);
int numwords = 1;
for(i = 0; i < len; i++) {
if(filename[i] == ' ') {
numwords++;
// eating up all spaces to not count following ' '
// dont checking if i exceeds len, because it will auto-stop at '\0'
while(filename[i] == ' ') i++;
}
}
In the above code i assume there will be at least one word in the filename (i.e. it wont be an empty string).
Now you can allocate memory for Argument1.
Argument1 = new char *[numwords];
After that you have two options:
use strtok (http://www.cplusplus.com/reference/clibrary/cstring/strtok/)
implement your function to split a string
That can be done like this:
int i,cur,last;
for(i = last = cur = 0; cur < len; cur++) {
while(filename[last] == ' ') { // last should never be ' '
last++;
}
if(filename[cur] == ' ') {
if(last < cur) {
Argument1[i] = new char[cur-last+1]; // +1 for string termination '\0'
strncpy(Argument1[i], &filename[last], cur-last);
last = cur;
}
}
}
The above code is not optimized, i just tried to make it as easy as possible to understand.
I also did not test it, but it should work. Assumptions i made:
string is null terminated
there is at least 1 word in the string.
Also whenever im referring to a string, i mean a char array :P
Some mistakes i noticed in your code:
in c/c++ " " is a pointer to a const char array which contains a space.
If you compare it with another " " you will compare the pointers to them. They may (and probably will) be different. Use strcmp (http://www.cplusplus.com/reference/clibrary/cstring/strcmp/) for that.
You should learn how to allocate dynamically memory. In c you can do it with malloc, in c++ with malloc and new (better use new instead of malloc).
Hope i helped!
PS if there is an error in my code tell me and ill fix it.