I have written some code in C, what it does is take an input of 2 strings A, B Where A is a normal string and B is a Sub string inside B. The program will "cut" out all the appearances of the sub sting B inside the string A. For example: A = "asdLEONasd", B = "asd" => C(Result) = "LEON".
everything seems to be working fine except after the output stage where it prints out a few unwanted characters.
Here are 2 examples for this: (the unwanted characters are underlined with a red pen)
Example 1
Example 2
The code:
#include <stdio.h>
#include <string.h>
void main()
{
int len1, len2;
puts("Input a length for a");
scanf("%d",&len1);
// Initializing A
char a[len1 + 1];
puts("Input a");
scanf("%s" ,a);
puts("Input length for b");
scanf("%d",&len2);
//Initializing B
char b[len2 + 1];
puts("Input b");
scanf("%s" ,b);
int i, j , k, count1 = 0, count2;
for(i = 0; i < len1; i++) //Loop that goes over string a
{
count2 = 0, k = 0;
for(j = i; j < len2 + i; j++) //Loop that goes over a part of a (from i to i + len2)
{
if(a[j] == b[k])
{
count2++; //Counting how many characters match with the sub string B
}
k++;
}
if(count2 == len2) //If counted characters = len2 then we know that we found the Sub string B in A
{
count1++; //Counting each appearance of B in A
for(j = i; j < len2 + i; j++) //Loop that marks cells that represent the sub string B in A
{
a[j] = '0'; //Marking cells that are the sub string b
}
}
}
if(!count1) //If count1 remained as 0 then B does not appear in A, which means the result is A
{
puts(a);
}
else
{
j = 0;
int len3 = len1 - count1 * len2; //Determining resulting array size
char c[len3]; // Initializing array C
//Filling array C accordingly
for(i = 0; i < len1; i++)
{
if(a[i] != '0')
{
c[j] = a[i];
j++;
}
}
puts(c);
}
}
What I find most weird is when my output array has a size of 4 for example, and it still prints the extra characters regardless the size.
I'm very curious as of why this happening and how can it be fixed?
You should think of a dumb implementation of puts as follows:
void puts(char *s)
{
while (*s) //if the current character isn't 0
{
putchar(*s); //print the character
++s; //move to the next character
}
putchar('\n');
}
Therefore, if the last character in your array isn't 0, the above loop will continue until there happens to be a 0 somewhere in the memory that follows.
If you're unable to add this terminating zero (as already mentioned by Bathsheba and yourself), you could use printf.
When using the printf family of functions, you can use the %s specifier to format a string (such as padding and limiting it's length).
char x[] = {'a', 'b', 'c', 'd'};
//print just abc
printf("%.*s\n", 3, x);
//print just abc
printf("%.3s\n", x);
//print just bcd
printf("%.*s\n", 3, x+1);
The problem was in the array C.
Changing char c[len3]; to char c[len3 + 1]; and adding an initialization c[len3] = '\0'; fixed this.
Before the third lines in the reciprocal of the program,that's right in front of this statement puts(c), if you add c[j]='\0', the problem you said will be solved.
Related
The problem: After the convert_tolower(words) function is completed I want to add a new word in the words array( if the words array has less than 5 words)..But I am getting either errors or unexpected results(e.g some weird characters being printed)...What i thought is shifting the elements of the words array and then work with pointers because I am dealing with strings.But I am having quite some trouble achieving that..Probably the problem is in lines
35-37
How I want the program to behave:
Get 5 words(strings) at most from user input
Take these strings and place them in an array words
Convert the elements of the array to lowercase letters
After the above,ask the user again to enter a new word and pick the position of that word.If the words array already has 5 words then the new word is not added.Else,the new word is added in the position the user chose.(The other words are not deleted,they are just 'shifted').
Also by words[1] I refer to the first word of the words array in its entirety
The code:
#include <stdio.h>
#include <string.h>
#define W 5
#define N 10
void convert_tolower(char matrix[W][N]);
int main() {
int j = 0;
int i = 0;
int len = 0;
char words[W][N] = {{}};
char test[W][N];
char endword[N] = "end";
char newword[N];
int position;
while (scanf("%9s", test), strcmp(test, endword)) {
strcpy(words[i++], test);
j++;
len++;
if (j == W) {
break;
}
}
convert_tolower(words);
printf("Add a new word\n");
scanf("%9s", newword);
printf("\nPick the position\n");
scanf("%d",position);
if (len < W) {
for (i = 0; i < W-1; i++) {
strcpy(words[i], words[i + 1]); /*Shift the words */
words[position] = newword;
}
}
for (i = 0; i < W; i++) {
printf("%s", words[i]);
printf("\n");
}
printf("End of program");
return 0;
}
void convert_tolower(char matrix[W][N]) {
int i;
int j;
for (i = 0; i < W; i++) {
for (j = 0; j < N; j++) {
matrix[i][j] = tolower(matrix[i][j]);
}
}
}
This initialization
char words[W][N] = {{}};
is incorrect in C. If you want to zero initialize the array then just write for example
char words[W][N] = { 0 };
In the condition of the while loop
while (scanf("%9s", test), strcmp(test, endword)) {
there is used the comma operator. Moreover you are using incorrectly the two-dimensional array test instead of a one-dimensional array
It seems you mean
char test[N];
//...
while ( scanf("%9s", test) == 1 && strcmp(test, endword) != 0 ) {
And there are used redundantly too many variables like i, j and len.
The loop could be written simpler like
char test[N];
//...
for ( ; len < W && scanf("%9s", test) == 1 && strcmp(test, endword) != 0; ++len )
{
strcpy(words[len], test);
}
In this call
scanf("%d",position);
there is a typo. You must to write
scanf("%d", &position);
Also you should check whether the entered value of position is in the range [0, len].
For example
position = -1;
printf("\nPick the position\n");
scanf("%d", &position);
if ( len < W && -1 < position && position <= len ) {
Also this for loop
for (i = 0; i < W-1; i++) {
strcpy(words[i], words[i + 1]); /*Shift the words */
words[position] = newword;
}
does not make a sense. And moreover this assignment statement
words[position] = newword;
is invalid. Arrays do not have the assignment operator.
You need to move all strings starting from the specified position to the right.
For example
for ( i = len; i != position; --i )
{
strcpy( words[i], words[i-1] );
}
strcpy( words[position], newword );
++len;
And it seems the function convert_tolower should be called for the result array after inserting a new word. And moreover you need to pass the number of actual words in the array.
convert_tolower(words, len);
The nested loops within the function convert_tolower should look at least the following way
void convert_tolower(char matrix[][N], int n) {
int i;
int j;
for (i = 0; i < n; i++) {
for (j = 0; matrix[i][j] != '\0'; j++) {
matrix[i][j] = tolower(( unsigned char )matrix[i][j]);
}
}
}
The main problem with your code was initially that you declared char *words[W][N], then tried to insert strings into this 2d array of pointers. Sparse use of organizing functions, and variables with large scopes than necessary made it hard to read. I think the best way to help you is to show you a working minimal implementation. Step 4 is not sufficiently specified. insert currently shift. It is not clear what should happen if you insert at position after empty slots, or if insert a position before empty slots and in particular if there are non-empty slots after said position.
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#define W 5
#define N 10
void convert(size_t w, size_t n, char list[][n]) {
for(size_t i = 0; i < w; i++) {
for(size_t j = 0; j < n; j++) {
list[i][j] = tolower(list[i][j]);
}
}
}
void insert(size_t w, size_t n, char list[][n], size_t pos, char *word) {
// out out of bounds
if(pos + 1 > w) return;
// shift pos through w - 2 pos
for(size_t i = w - 2; i >= pos; i--) {
strcpy(list[i + 1], list[i]);
if(!i) break;
}
// insert word at pos
strcpy(list[pos], word);
}
void print(size_t w, size_t n, char list[][n]) {
for (size_t i = 0; i < w; i++) {
printf("%u: %s\n", i, list[i]);
}
}
int main() {
char words[W][N] = { "a", "BB", "c" };
convert(W, N, words);
insert(W, N, words, 0, "start");
insert(W, N, words, 2, "mid");
insert(W, N, words, 4, "end");
insert(W, N, words, 5, "error")
print(W, N, words);
return 0;
}
and the output (note: "c" was shifted out as we initially had 3 elements and added 3 new words with valid positions):
0: start
1: a
2: mid
3: bb
4: end
I"m trying to store int array as a str and display it but in the reverse order.
Its only while printing the str that i get junk.
What is wrong in my code?
int main() {
int a[] = { 1, 2, 3 }; // Output should be 321 (char)
int size = sizeof(a) / sizeof(int);
char str[size + 1];
int i;
for (size = size - 1; size >= 0; size--) {
sprintf(&str[size], "%d", a[size]);
//printf("%c\n", str[size]);
}
printf("%s\n", str); // I get garbage.
}
I modified your solution with several bug fixes. For starters, you can't assume that your integer array will only hold single digit values.
And that for loop as you have it:
for(size=size-1;size >= 0;size--)
Is very suspicious looking. (the index variable is the thing its based off?)
Simple solution
This is likely what you meant:
for(i = 0; i < size; i++) {
sprintf(&str[i],"%d", a[size-1-i]);
}
str[size] = '\0';
Or this:
str[size] = '\0';
for(i = size-1; i <= 0; i--) {
sprintf(&str[i],"%d", a[size-1-i]);
}
Better solution
I'm not sure what you are expecting to do if an integer within the a array is negative. So the - sign will just get inserted into str inplace.
The solution I have will first count how many chars are needed for each integer in a. Then it will allocate the str buffer with that length (+1 for null char).
Then we make use of the return value from sprintf to figure out where to concatenate onto. We could use strcat, but this is likely faster.
int main() {
int j = 0;
int a[] = { 1,2,3 }; // Output should be 321 (char)
int size = sizeof(a) / sizeof(int);
int length = 1; // +1 for final null char
// Count the size of characters needed for each integer
// Do a dummy sprintf and use its return value to figure out how many chars are needed
for (int i = 0; i < size; i++) {
char tmp[sizeof(int) * 5]; // sizeof(int)*5 is big enough to hold any integer including a negative value
length += sprintf(tmp, "%d", a[i]); // utilize the return value from sprintf and add it to the running length
}
char str[length];
str[0] = '\0'; // initially null terminate our string
// reverse print chars from a into str
for (int i = 0; i < size; i++) { // use i as index variable, not size
j += sprintf(str + j, "%d", a[size - 1 - i]);
}
printf("%s\n", str);
}
Alternative solution, closer to original posts, and clearly not trying to address the general problem (assume values are single digit):
int a[]={1,2,3}; // Output should be 321 (char)
int size = sizeof(a)/sizeof(int);
char str[size+1];
for(int i=0; i<size ; i++) {
str[size-1-i] = ‘0’ + a[i];
}
str[size] = 0;
printf("%s\n", str); // I get garbage.
}
Taking advantage of the assumed input value, converting each int to character representation at the reverse position.
I'm learning C with the CS50 course problem set 2, using the crypt function to brute force guess a password. Currently writing a function that prints all possible strings of a certain length, eg:
aa
ab
...
az
ba
...
zy
zz
I've written a fairly simple recursive function to do so:
#include <cs50.h>
#include <stdio.h>
#include <crypt.h>
#include <string.h>
void stringcycler(int n, int passLength, char *pass)
// Scrolls through all lowercase letter combinations for a string of length passLength
// Expects an integer value of the length of the strng as both n and passLength
// Also expects a char* array of length passLength with all chars set to 'a' (and a null character)
{
if(n != 0)
{
for(pass[passLength - n] = 'a'; pass[passLength - n] < 'z'; pass[passLength - n]++)
{
stringcycler(n-1, passLength, pass);
printf("%s\n", pass);
// return 0;
}
}
}
int main()
{
// Initialise char *c, and scroll through letters
int passLength = 2; // The number of characters you want to brute force guess
char pass[passLength + 1]; // Add 1 for the null character
int i;
for(i = 0; i < passLength; i++) pass[i] = 'a'; // Set every char in pass to 'a'
pass[passLength] = '\0'; // Set null character at the end of string
stringcycler(passLength, passLength, pass);
return 0;
}
It works for the most part, but only goes to yz. Whenever it sees a z it basically skips, so it goes to yz, then never does za to zz. If I add an = to the for loop line:
pass[passLength - n] < 'z';
ie.
pass[passLength - n] <= 'z';
Then it prints '{' characters in the mix. Any help? And another question is, how can I change this to work for all combos of upper and lower case too, is there a neat way of doing it?
You print after you return from you recursion, but you should print when the recursion has reached the end (or beginning, in your case) of the string. In other words, printing should be an alternative branch to recursing:
void stringcycler(int n, int len, char *pass)
{
if (n != 0) {
for (pass[len - n] = 'a'; pass[len - n] <= 'z'; pass[len - n]++) {
stringcycler(n - 1, len, pass);
}
} else {
printf("%s ", pass);
}
}
The if part constructs the strings as it recurses further down. The else part does something with the constructed string. (Of course, you must include 'z' in your loop. Your original code only prints the z in the last place, because it prints after ther recursion returns, which means thet the char buffer is in a condition that wouldn't (re-)enter the loop.)
Below is a generic backtracking algorithm for generating the password. The idea here is to imagine filling the slots for a given char array a. We will be generating the possible candidates for the given position k for the array a. I have taken the candidates as lower case ascii letters a-z and upper case ASCII letters A-Z. If you want to include other ASCII characters, just modify the construct_candidates function accordingly.
Once the array is filled i.e. k becomes PASS_LEN, we know we have generated the password, we can process it however we like, I have just printed the password here.
The value of PASS_LEN macro can be adjusted to generate password of any desired length.
#include <stdio.h>
#include <stdlib.h>
#define PASS_LEN 2
static char* construct_candidates (char a[], int k, int *count)
{
/* Lower case ASCII */
int min1 = 97;
int max1 = 122;
/* Upper case ASCII */
int min2 = 65;
int max2 = 90;
*count = (max1 - min1 + 1) + (max2 - min2 + 1);
char *cand = calloc(*count, sizeof(char));
if (cand == NULL) {
printf("malloc failed\n");
return NULL;
}
int idx = 0;
for (int i = min1; i <= max1; i++) {
cand[idx] = i;
idx++;
}
for (int i = min2; i <= max2; i++) {
cand[idx] = i;
idx++;
}
return cand;
}
static void backtrack(char a[], int k)
{
int i;
if (k == PASS_LEN) {
for (i = 0; i < PASS_LEN; i++) {
printf("%c", a[i]);
}
printf("\n");
return;
}
int cand_count = 0;
char *cand = construct_candidates(a, k, &cand_count);
if (cand == NULL) {
printf("Failed to get candidates\n");
return;
}
for (i = 0; i < cand_count; i++) {
a[k] = cand[i];
backtrack(a, k + 1);
}
free(cand);
}
int main()
{
char a[PASS_LEN] = {'\0'};
backtrack(a, 0);
}
I'm trying to make a program in C that reads a word and prints if there are any duplicates and if so the number of occurrences. It works (as you can see in the attached pic) but once a letter has been printed I don't want it to reprint the same letter.
I've tried storing the duplicate chars in an array and then comparing the new duplicate to the duplicate array but it doesn't seem to be working.
Anyone know a simple way to not reprint?
#include <stdio.h>
#include <string.h>
int main(void) {
char word[100];
int x, i, j, freq, duplicates;
printf("Enter a word>\n");
scanf("%s", word);
x = strlen(word);
duplicates = 0;
freq = 1;
for(; i < x; i++) {
j = 0;
for(; j < x; j++) {
if ((word[i] == word[j]) && (i != j)) {
freq = freq + 1;
}
}
if (freq >= 2) {
printf("Duplicate letter: %c, Occurences: %d\n", word[i], freq);
duplicates = 1;
freq = 1;
}
}
if (duplicates < 1) {
printf("No duplicates found\n");
}
return 0;
}
Your problem here is in fors that look for the duplicate letter
The first one should go throw the string to look for all letters:
for (i = 0; i < x; i++) {
The second should look for the occurrence of the same character:
for (j = i; j < x; j++) {
Its because it runs once on each time it finds t and e respectively. One solution would be to find all occurrences of that char in the char array after printing the duplicate notification and removing it.
char * removeLetterFromArray(int toBeRemoved, char* string, int stringLength){
char * newString = malloc(stringLength * sizeof(char));
for(int i = 0; i < toBeRemoved; i++){
newString[i] = string[i];
}
for(int i = toBeRemoved; i < stringLength; i++){
newString[i] = string[i + 1];
}
return newString;
}
that code should remove the letter that you define the index of with toBeRemoved
So after you find a letter that has a duplicate loop through the code to find all places that letter occurs and pass them indexs to the above method.
If you do not wish to use the above method another option would be to create an array of letters that have already been output and ignore these letters in the future.
Here is my code. I need to find out the number of times a given word(a short string) occurs in a sentence(a long string).
Sample Input: the
the cat sat on the mat
Sample Output: 2
For some reason the string compare function is not working and my output is coming as zero. Kindly ignore the comments in the code as they have been put to debug the code.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(){
char word[50];
gets(word);
int len = strlen(word);
//printf("%d",len);
char nword[len];
char s[100];
strcpy(nword,word);
puts(nword);
printf("\n");
gets(s);
//printf("%d",strlen(s));
char a[50][50];
int i,j,k;
j = 0;
for(i=0;i<strlen(s);i++)
{
a[i][j] = s[i];
printf("%c",a[i][j]);
if(s[i] == ' ')
{
j++;
printf("\n");
}
}
printf("%d",j);
k = j;
//printf("\nk assigned\n");
j = 0;
//printf("j equal to zero\n");
int count = 0;
int temp = 0;
//printf("count initialized.\n");
for(i=0;i<k;i++)
{
if(strcmp(a[i],nword) == 0)
count++;
}
printf("\n%d",count);
return 0;
}
Your main problem is with this loop for numerous reasons
int i,j,k;
j = 0;
for(i=0;i<strlen(s);i++)
{
a[i][j] = s[i];
printf("%c",a[i][j]);
if(s[i] == ' ')
{
j++;
printf("\n");
}
}
Firstly you've got your indexes into a backwards - a[i][j] means the i-th string and the j-th character, but since you're incrementing j for each word you want it the other way around - a[j][i].
Secondly you can't use i for both indexing into s and a. Think about what happens when you are building the second string. In your example input the second word starts when i is 4 so the first character will be stored as a[1][4]=s[4] which leaves a[1][0] to a[1][3] uninitialised. So you have to use a 3rd variable to track where you are in the other string.
When you hit a space, you don't want to add it to your word as it won't match later on. You also need to add in a null-terminator character to the end of each string or else your code won't know where the end of the string is.
Putting the above together gives you something like this:
int i,j,k;
k = j = 0;
for(i=0;i<strlen(s);i++)
{
if(s[i] == ' ')
{
a[j][k] = '\0';
j++;
k=0;
printf("\n");
}
else
{
a[j][k] = s[i];
printf("%c",a[j][k]);
k++;
}
}
a[j][k]='\0';
The problem is that a is a two-dimentional array and you reference it as a one dimention. Maby you use a 2-dimentional array to represent i=line, j=character. If you keep this idea then you'll have to do this:
j=0;
for(i=0;i<k;i++)
{
if(strcmp(a[i][j],nword) == 0)
count++;
j++;
}
But then it will be difficult to detect words that are split in half. I'd recommend keeping a as a one dimentional array. Copy the contents of s[i] serially and when you want to distinguish lines use the \r\n operator.
I think you use your 2-dimensional array wrong. a[0][j] should be the first word from s[i]. But what you are doing is a[i][0] = s[i] which makes no sense to me.
Best regards
I would implement this using the functions strtok() and strcmp():
int main(void)
{
char word[] = "the"; /* the word you want to count*/
char sample[] = "the cat sat on the mat"; /* the string in which you want to count*/
char delimiters[] = " ,;.";
int counter;
char* currentWordPtr;
/* tokenize the string */
currentWordPtr = strtok(sample, delimiters);
while(currentWordPtr != NULL)
{
if(strcmp(word, currentWordPtr) == 0)
{
counter++;
}
/* get the next token (word) */
currentWordPtr = strtok(NULL, delimiters);
}
printf("Number of occurences of \"%s\" is %i\n", word, counter);
return 0;
}