Question

What will the value of the string s1 after the following statements have been executed?

strcpy(s1, "computer");
strcpy(s2, "science");
if(strcmp(s1, s2) < 0){
    strcat(s1, s2);
}
else{
    strcat(s2, s1);
}
s1[strlen(s1) - 6] = '\0';

I know the answer is "Computers" but why? Can someone explain to me how to approach this problem?

Answer 1

strcpy(s1, "computer"); ->  s1 is "computer"
strcpy(s2, "science");  ->  s2 is "science"
if(strcmp(s1, s2) < 0){ ->  if s1 is less than s2(alphabetically). computer is less than science because c comes before s
    strcat(s1, s2); //  s1 becomes "computerscience"
}
else{
    strcat(s2, s1);
}
s1[strlen(s1) - 6] = '\0';      // strlen(s1) is 15. 15-6=9.  so, s1[9] = '\0'.  so, s1 becomes computerscience\0ience"

all characters after \0 are ignored. because \0 indicates end of string.
that's value s1 prints  "computers"