Question

Implement a C program unique.c that recreates the functionality of the uniq tool by reading the input line by line and dropping each l ine that is identical to the line immediately before it. On the input abc abc abc your program should output abc abc the same output that uniq would produce. While not strictly necessary for this step, it is important as a basis for subsequent steps that you read the entire input and store it as a sequence of lines. Specifically, you should represent the input text as a struct that stores the number of lines in the input and the text as a field of type char . This char ** points to a dynamically allocated array of char pointers. Each of these pointers points to a dynamically allocated char array that stores a single input line. You need to deal with two potential complications: 1. There is no upper limit on the length of each input line. Normally, this would force you to allocate an array of a certain minimum size for each line and then resize this array if it is not large enough to hold the current line. Thankfully, the getline function can be used in a fashion that does this work for you. Read its manpage to find out how you can get it to return a dynamically allocated character array that stores the read input line 2. You do not know the number of input lines in advance. Thus, you have to allow the array of pointers to the individual lines to grow. To do this, you need to allocate a larger array once your current array is full, copy the elements of the current array to the new array, and finally free the current array and start using the new array. In order to avoid a quadratic running time resulting from excessive copying, the new array you allocate should be twice as big as the current array. For checking consecutive input lines that are the same, you can use the strcmp standard library function Read it s manpage to find out how to use it. An important requirement for your program is that it should not leak any memory. Since all memory still held by a process is released when the process exits, there is technically no effort required on your part to meet this requirement. However, it is important for you to practice how to manually manage allocated memory over the course of a longer-running program. Thus, for full marks you need to explicitly release all memory allocated to your program before the program exits. Specifically you need to call free on the char array holding each line and on the array of char pointers referring to these char arrays. In later steps, you will add a few more dynamically allocated arrays that you will also have to release.

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include<string.h>

int main(void) {
int i,count=1,len=5,j,value,k;
// Allocate memory of size 5
char **array1 = malloc(len * sizeof(char *));
//another array for reallocation
char **array2;
size_t size = 10;
ssize_t nread;
for(i=0;i<len;i++){
array1[i] = malloc(3* sizeof(char));
// Adjusts the size of array[i] automatically
printf("\n String");
nread = getline(&array1[i],&size,stdin);
count++;
if(count == len){
//new array of size double of the original array
array2 = (char **)realloc(array1, sizeof(char *) * 2*len);
for(i=len-1;i<(2*len);i++){
array2[i] = malloc(3* sizeof(char));
// Adjusts the size of array[i] automatically
printf("\n String");
nread = getline(&array2[i],&size,stdin);
count++;}
len = 2*len;
}

}
//printf("\n %d",count);
value = count-1;
//delete adjacent duplicate values
for(i = 0; i < value; i++)
{
for(j = i+1; j < value; )
{
if(strcmp(array2[j],array2[i])==0)
{
for(k = j; k < value; k++)
{
strcpy(array2[k],array2[k+1]);
}
value--;
}
else
{
j++;
}
}
}
for(i = 0; i < value; i++)
printf("Your string: %s\n", array2[i]);

return 0;
}