C++ :

#include <bits/stdc++.h>
using namespace std;

//判断字符串是否能够接龙 
bool fun(string s){
	string a[30],w="";
	int i,k = 0;
	for(i = 0;i < s.size();i++){
		if(s[i] != ' '){
			w = w + s[i];
			if(i == s.size() - 1 || s[i+1] == ' '){
				a[k] = w;
				if(k != 0 && a[k][0] != a[k-1][a[k-1].size()-1]){
					return false;
				}
				k++;
				w = "";
			}
		}
	}
	
	return true;
}

int main() {
	string s;
	getline(cin,s);
	if(fun(s)){
		cout<<"Y";
	}else{
		cout<<"N";
	}
}

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.nextLine();
		String str1 = "" + str.charAt(0);
		for(int i = 0;i <str.length()-1;i++) {
			if(str.charAt(i) == ' ' && str.charAt(i+1) == ' ') {
				continue;
			}else {
				str1 += str.charAt(i+1);
			}
		}
		String str2 = str1.trim();
		String[] arr = str2.split(" ");
		char f = 'N';
		for(int i = 0 ;i < arr.length - 1;i++) {
			if(arr[i].charAt(arr[i].length()-1) == arr[i+1].charAt(0)
//					&& arr[0].charAt(0) != arr[arr.length-1].charAt(arr[arr.length-1].length()-1
//					)
					)
			{
				f = 'Y';
			}else {
				f = 'N';
				break;
			}
		}
		System.out.println(f);
	}

}