Checking if a list of strings can be chained

Question

Question

Implement a function bool chainable(vector v), which takes a set of strings as parameters and returns true if they

Answer 1

Here's a simple program to do this iteratively:

#include <string>
#include <vector>
#include <iostream>

using std::vector;
using std::string;

bool isChained(vector<string> const& strngs)
{
    if (strngs.size() < 2) return false;      //- make sure we have at least two strings
    if (strngs.front().empty()) return false; //- make sure 1st string is not empty

    for (vector<string>::size_type i = 1; i < strngs.size(); ++i)
    {
        string const& head = strngs.at(i-1);
        string const& tail = strngs.at(i);
        if (tail.empty())  return false;
        if (head[head.size()-1] != tail[0])  return false;
    }

    return true;
}

int main()
{
    vector<string>  chained;
    chained.push_back("ship");
    chained.push_back("petal");
    chained.push_back("lion");
    chained.push_back("nick");

    vector<string>  notChained;
    notChained.push_back("ship");
    notChained.push_back("petal");
    notChained.push_back("axe");
    notChained.push_back("elf");

    std::cout << (isChained(chained) ? "true" : "false") << "\n";     //- prints 'true'
    std::cout << (isChained(notChained) ? "true" : "false") << "\n";  //- prints 'false'

    return 0;
}

Answer 2

if you replace petal and lion with pawn and label, you still have:
starts:s,p,l,n
ends: p,l,n,k

You're algorithm decides its chainable, but they aren't.
The problem is you are disconnecting the first and last letters of each word.

A recursive backtracking or dynamic programming algorithm should solve this problem.