Excessive arguments error for recursive reverse string method

Question

I'm trying to program a recursive function that prints the reverse of the string, however, the compiler keeps saying it has too many arguments. What is wrong with this recursive program?

#include <iostream>
using namespace std;

void reverseDisplay (const string& s)
{

    int length=s.size()-1;
    if (length==0)
        return;

    reverseDisplay(s, length);
}

void reverseDisplay (const string& s, int n)
{
    if(n==1)
        cout <<s[n];

    else { 
        cout << s[n];
        reverseDisplay(s, n-1);
    }
}

int main()
{
    string s="12345";
    reverseDisplay(s);


    return 0;
}

And also, the if statement in reverseDisplay (const string& s, int n) should be if(n==0) — Roun
– Roun, Commented Oct 7, 2013 at 1:31

user1508519 · Accepted Answer · 2013-10-07 01:13:08Z

5

Try a forward declaration:

void reverseDisplay (const string& s, int n);

Put this before void reverseDisplay (const string& s).

answered Oct 7, 2013 at 1:13

user1508519

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Comments

Eric Jablow · Accepted Answer · 2013-10-07 02:19:06Z

To solve a problem recursively, you want a function that calls itself, and a stopping condition. Using the size, however, is not necessary. Also, it will be more useful if you have a method that reverses a string; leave printing for later. Now, the typical way to reverse a string in any language is this bit of pseudocode:

reverse("abcd")            -->
        string suffix
reverse("abcd", ""       ) -->  
reverse("bcd",  "a" + "" ) ==
reverse("bcd",  "a"      ) --> string, suffix
reverse("cd",   "b" + "a") ==
reverse("cd",   "ba"     ) -->
reverse("d",    "c" + "ba")==
reverse("d",    "cba"    ) -->
reverse("", "d" + cba")
reverse("", "dcba")       --> Let this be the stopping condition.

So, we do this:

string reverse(const string original, string suffix);

string reverse(const string original) { 
    return reverse(original, new string);
} 

string reverse(const string original, string suffix) { 
    if (original.size()) {
         auto first = original.first();
         return reverse(original.substr(1), suffix.insert(0, 1, first));
    } else {
        return suffix;
    }
}

I could probably have made some of these variables references.

Jamal · Accepted Answer · 2014-12-15 22:27:17Z

2

You're not really doing recursion in reverseDisplay(const string& s). You're calling the other reverseDisplay(), which takes two arguments. This makes them overloaded, so the compiler will call the one that matches the arguments (or display an error if no such overload exists).

Here's a working recursive solution with just one display function:

#include <iostream>
#include <string>

void reverseDisplay(std::string const& s, std::size_t n)
{
    if (n == -1)
    {
        return;
    }

    std::cout << s[n];
    reverseDisplay(s, n-1);
}

int main()
{
    std::string s = "12345";
    std::size_t size = s.size();
    reverseDisplay(s, size-1);
}

edited Dec 15, 2014 at 22:27

answered Oct 7, 2013 at 1:11

Jamal

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3 Comments

user1508519 Over a year ago

Which should be before the other one, anyway.

Cyclonecode Over a year ago

Why use recursion at all for this? Why not use a simple for loop from length - 1 downto 0?

Jamal Over a year ago

@KristerAndersson: I wasn't addressing that. In any event of recursion, the OP's code isn't doing that there. The reverseDisplay() with two arguments is doing this properly, though.

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