Puts and Gets in c++ [closed] - c++

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I know what puts and gets do, but I don't understand the meaning of this code.
int main(void) {
char s[20];
gets(s); //Helloworld
gets(s+2);//dog
sort(s+1,s+7);
puts(s+4);
}
Could you please help me to understand?

Answer 1

Draw it on paper, along these lines.
At first, twenty uninitialised elements:
| | | | | | | | | | | | | | | | | | | | |
gets(s):
|H|e|l|l|o|w|o|r|l|d|0| | | | | | | | | |
gets(s+2):
|H|e|d|o|g|0|o|r|l|d|0| | | | | | | | | |
^
|
s+2
sort(s+1, s+7):
|H|0|d|e|g|o|o|r|l|d|0| | | | | | | | | |
^ ^
| |
s+1 s+7
puts(s+4):
|H|0|d|e|g|o|o|r|l|d|0| | | | | | | | | |
^
|
s+4

Answer 2

The best thing to say about the code is that it is very bad. Luckily, it is short but it is vulnerable, unmaintainable and error prone.
However, since the previous is not really an answer, let's go through the code, assuming the standard include files were used and "using namespace std;":
char s[20];
This declares an array of 20 characters with the intent of filling it with a null-terminated string. If somehow, the string becomes larger, you're in trouble
gets(s); //Helloworld
This reads in a string from stdin. No checks can be done on the size. The comment assumes it will read in Helloworld, which should fit in s.
gets(s+2);//dog
This reads in a second string from stdin, but it will overwrite the previous string starting from the third character. So if the comment is write, s will contain the null-terminated string "Hedog".
sort(s+1,s+7);
This will sort the characters in asserting ascii value from the second up to the seventh character. With the given input, we already have a problem that the null-character is on the sixth position so it will be part of the sorted characters and thus will be second, so the null-terminated string will be "H".
puts(s+4);
Writes out the string from the fifth position on, so until the null-charater that was read in for "Helloworld", but then overwritten and half-sorted. Of course input can be anything, so expect surprises.

Answer 3

gets(s); //Helloworld -- reads a string from keyboard to s
gets(s+2);//dog -- reads a string from keyboard to s started with char 2
sort(s+1,s+7); -- sorts s in interval [1, 7]
puts(s+4); -- writes to console s from char 4
gets(s); //Helloworld --> s=Helloworld
gets(s+2);//dog --> s=Hedog
sort(s+1,s+7); --> s=Hdego
puts(s+4); --> console=Hdego