Question

2. This question is about processing strings 2.1 [4 marks] Given a string str, we can calculate a checksum of the string by summing up the ASCII codes of the characters in the string. For example, the checksum of a string "apple" is 530, which equals to 'a' + 'p' + 'p' + 'l' + 'e' = 97 + 112 + 112 + 108 + 101. Write a function int calculate_checksum(char str[] that calculates and returns the checksum of the string str 2.2 [6 marks] Given a string str that contains an English sentence, we can compute an abstract of the sentence by replacing every word in the sentence with its opening and ending characters. For example, if str = "Algorithm is a fun subject", then its abstract is "Am is aa fn st", where the words "Algorithm", "is", "a", "fun", and "subject" are replaced with "Am", "is", "aa", "fn", and "st", respectively. Write a function char *compute_abstract (char str[]) that computes and returns the abstract of string str. For example, if the function input "Algorithm is a fun subject", the function should return a char pointer point- str ing to a string "Am is aa fn st". You may assume that: There are only English letters and space characters (' ') in str. Every word in str only consists of English letters. There is only one space character between any two adjacent words in str String str contains at least one word. String str does not start or end with space characters. You need to add suitable #include lines if you use any library functions. Note: You may not modify the input string str. You need to allocate memory properly for the abstract string. If you are unsure about how to do this, you may write an alternative function void compute_abstract_alt(char str[], char abs]) that computes the abstract of string str and stores it in another string abs. For example, if str "Algorithm is a fun subject", after calling this function, abs should become "Am is aa fn st". You may assume that abs has sufficient space to store the abstract You just need to write one of the two functions above. You do not need to write both. If you write function compute_abstract, the full mark of this sub-question is 6. If you write function compute_abstract_alt, the full mark of this sub-question is 3.

Answer 1

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#include<stdio.h>

#include<string.h>

#include<stdlib.h>

int calculate_checksum(char str[]);

char *compute_abstract(char str[]);

int main(){

char str[] = "apple";

int checksum = calculate_checksum(str);

printf("Checksum is: %d\n", checksum);

char str1[] = "Algorithm is a fun subject";

char *result = compute_abstract(str1);

printf("%s\n", result);

free(result);

return 0;

}

int calculate_checksum(char str[]){

int i=0;

int sum = 0;

while(str[i]!='\0'){

sum += str[i];

i++;

}

return sum;

}

char *compute_abstract(char str[]){

int wc = 0;

int i=0;

while(str[i]!='\0'){

if(str[i]==' ')

wc++;

i++;

}

char *new_str = (char *)malloc(wc + wc*2*sizeof(char));

int k=0;

char *token = strtok(str, " ");

while(token!=NULL){

new_str[k++] = token[0];

new_str[k++] = token[strlen(token)-1];

new_str[k++] = ' ';

token = strtok(NULL, " ");

}

new_str[k] = '\0';

return new_str;

}