Question

[c++] Write a recursive function takes a word string as input argument and reverse the word. Print out the results of recursive calls. Also write a main program accepts input from the user and then call the recursive function.

Example:
Enter a word: hello
h
eh
leh
lleh
olleh

Answer 1

#include<iostream>
using namespace std;


void reverseInput(string x) {
cout << x << endl;
if (x>word.length(1)) {
reverseInput(word.length(x)-word.length((0));
}
}

int main()
{
string word;
cout << "Enter a word: ";
cin >> word;
cout << reverseInput(word) << endl;

return 0;

}

I'm not sure how to write the actual recursive part using strings

Answer 2

http://ideone.com/crsWI

Answer 3

I did it recursively, but I still believe this is a horrible way to reverse a string. There's probably a library function to accomplish this, and if there isn't then I'm sure an iterative procedure would do the job better.

Answer 4

Here's the proper way to do it: http://ideone.com/ewIsg#ul_inouterr

Answer 5

I just can't figure out how to output the 'recursive calls' as in the example.

http://ideone.com/oxrCv
http://ideone.com/ewIsg#li_ewIsg

Answer 6

maybe adhokshaj knows :-D

Answer 7

This is all I could do: http://ideone.com/cnH7r

Answer 8

maybe it's because I did it backwards :-P

Answer 9

It can be done in one line in Python, with no fancy pants recursion :-P
http://ideone.com/19Hse

Answer 10

It can be done in most languages without recursion, and in many languages that's more efficient. Notably, in functional languages that optimize tail calls, it can be done equally efficiently recursively. And it's worth it to learn how to think recursively. It's very different, but it can be a beautiful way to approach problems.

Answer 11

//initialize function
test();
private function test():void{
trace("this function will call itself recursively");
test();
}

Answer 12

recursive funtions tend to be faster than for loops which can be a problem becasue if you have other functions that are slower but provide data to a recursive function you might find yourself with unexpected data or an errror.......this is unusual but within reality I think.

Answer 13

#include <iostream>
#include <string>

using namespace std;

void reverseString( string text )
{
if( text.length() == 0 )
return;
string character = text.substr( 0, 1 );
reverseString( text.substr( 1 ) );
cout << character;
}

int main( int argc, char *argv[] )
{
reverseString( "One if by land." );
cout << endl;
return 0;
}

Answer 14

^Does not return recursive calls :/

Answer 15

I'm sure shadowfiend could do easily do this :-D

Answer 16

Sorry about that. All that would need to done is to pass down an empty string, append character to it, and cout it instead of character.

Answer 17

Hey, I have a question.

Answer 18

int main(int argc, char** argv).... what are you pointing to? Why are you using arguments? Thanks!!

Answer 19

int main(int argc, char** argv) (or more often you might find it as int main(int argc, char *argv[]) but it's basically the same thing) is just a convention I use, and the program will work just as right if you just leave the parameters of main empty like int main().

Writing argc and argv lets your program access the arguments you pass it when you call it using the terminal: argc is the number of arguments you pass it, which is 1 by default if you simply call the program name, and argv[] is the argument vector, and it's zeroth element is the file path of your program, and any subsequent elements in argv depend on whether you passed it arguments.

Your code does not really use argc or argv, so if I left it out like this: http://ideone.com/AZjsi it will still work the same way.

Answer 20

Though it's worth mentioning that the two parameters, and the int return type, are theoretically the only way to write valid C++. C doesn't care, but C++ I believe requires those parameters and that return type (compilers generally don't choke if you don't have them, though).