Go: package main

import (
    "bufio"
    "os"
    "fmt"
)

var sc = bufio.NewScanner(os.Stdin)

/**************  Cell  *****************/
type Cell struct {
    item interface{}
    next *Cell
    prev *Cell
}

func NewCell(x interface{}, ne *Cell, pr *Cell) *Cell {
    newCp := new(Cell)
    newCp.item = x
    newCp.next = ne
    newCp.prev = pr
    return newCp
}
/************  End Cell  ***************/

/**************  Queue  ****************/
type Queue struct {
    size int
    front *Cell
    rear *Cell
}

func NewQueue() *Queue {
    return new(Queue)
}

func (q *Queue) Push(x interface{}) {
    newNode := NewCell(x, nil, nil)
    if q.size == 0 {
        q.front = newNode
        q.rear = newNode
    } else {
        newNode.prev = q.rear
        q.rear.next = newNode
        q.rear = newNode
    }
    q.size++
}

func (q *Queue) PopLeft() interface{} {
    if q.size == 0 {
        return nil
    } else {
        x := q.front.item
        if q.size == 1 {
            q.front = nil
            q.rear = nil
        } else {
            q.front = q.front.next
            q.front.prev = nil
        }
        q.size--
        return x
    }
}

func (q *Queue) IsEmpty() bool {
    return q.size == 0
}

func (q *Queue) Length() int {
    return q.size
}

type State struct {
    color string
    cnt int
}

func main() {
    for {
        sc.Scan()
        init := sc.Text()
        if init == "0" {
            break
        }
        bfs(init)
    }
}

func bfs(init string) {
    dic := make(map[string]int)
    que := NewQueue()
    que.Push(State{init, 0})
    length := len(init)
    isSolved := false
    for !que.IsEmpty() {
        state := que.PopLeft().(State)
        _, ok := dic[state.color]
        if ok {
            continue
        } else {
            dic[state.color] = state.cnt
        }

        if isSingleColor(state.color) {
            fmt.Println(state.cnt)
            isSolved = true
            break
        }

        for i := 0;i < length - 1; i++ {
            color1, color2 := string(state.color[i]), string(state.color[i + 1])
            if color1 != color2 {
                color3 := other(color1, color2)
                if i <= length - 2 {
                    que.Push(State{state.color[:i] + color3 + state.color[i + 2:], state.cnt + 1})
                } else {
                    que.Push(State{state.color[:i] + color3, state.cnt + 1})
                }
            }
        }
    }
    if !isSolved {
        fmt.Println("NA")
    }
}

func other(color1, color2 string) string {
    if color1 == "r" {
        if color2 == "g" {
            return "bb"
        } else if color2 == "b" {
            return "gg"
        }
    } else if color1 == "g" {
        if color2 == "r" {
            return "bb"
        } else if color2 == "b" {
            return "rr"
        }
    } else if color1 == "b" {
        if color2 == "r" {
            return "gg"
        } else if color2 == "g" {
            return "rr"
        }
    }
    return ""
}

func isSingleColor(color string) bool {
    for _, c := range color {
        if string(c) != string(color[0]) {
            return false
        }
    }
    return true
}

C++: #include<iostream>
#include<queue>
#include<set>
using namespace std;

typedef pair<string,int> P;

int main()
{
  for(;;)
    {
      string str;
      cin>>str;
      if(str=="0")
	break;
      queue<P> qu;
      set<string> hash;       
      qu.push(P(str,0));
      hash.insert(str);
      int ans=-1;
      while(!qu.empty())
	{
	  P a= qu.front();
	  qu.pop();
	  int count=0;
	 
	  string t=a.first;
	  for(int i=0;i<t.size()-1;i++)
	    {
	      if(t[i]!=t[i+1])
		{
		  string x=t; 
		  if((x[i]=='r'&&x[i+1]=='g') ||(x[i]=='g'&&x[i+1]=='r'))
		    x[i]='b',x[i+1]='b';
		  if((x[i]=='r'&&x[i+1]=='b') ||(x[i]=='b'&&x[i+1]=='r'))
		    x[i]='g',x[i+1]='g';
		  if((x[i]=='g'&&x[i+1]=='b') ||(x[i]=='b'&&x[i+1]=='g'))
		    x[i]='r',x[i+1]='r';
		  if(hash.find(x)==hash.end())
		    {
		      hash.insert(x);
		      qu.push(P(x,a.second+1));
		    }
		}
	      else
		{
		  count++;
		}
	    }
	  if(count==t.size()-1)
	    {
	      ans=a.second;
	      break;
	    }
	}
      if(ans==-1)
	  cout<<"NA"<<endl;            
	else
	  cout<<ans<<endl;            
    }

}

C++: #include <bits/stdc++.h>

#define FOR(i, n, m) for(int i = (n);i < (m);i++)
#define REP(i, n) for(int i = 0;i < (n);i++)
#define PII pair<int, int>

using namespace std;

string worm;

int all(string a){
    char b = a[0];
    int cnt = 0;
    for(int i = 1;a[i] != '\0';i++){
        if(a[i] != b)
            cnt++;
    }
    return cnt;
}

int solve(){
    queue< pair<string, int> > que;
    que.push(pair<string, int>(worm, 0));

    if(all(worm) == 0){
        return 0;
    }

    while(que.size()){
        string worm1 = que.front().first;
        int num = que.front().second;
        que.pop();

        if(all(worm1) == 1){
            continue;
        }else if(all(worm1) == 0){
            return num;
        }

        if(num > 9){
            return -1;
        }
        for(int i = 0;i < strlen(worm1.c_str())-1;i++){
            string tmp = worm1;
            if(worm1[i] != worm1[i+1]){
                if((worm1[i] == 'b' && worm1[i+1] == 'g') || (worm1[i] == 'g' && worm1[i+1] == 'b')){
                    tmp[i] = tmp[i+1] = 'r';
                    que.push(pair<string, int>(tmp, num+1));
                }else if((worm1[i] == 'b' && worm1[i+1] == 'r') || (worm1[i] == 'r' && worm1[i+1] == 'b')){
                    tmp[i] = tmp[i+1] = 'g';
                    que.push(pair<string, int>(tmp, num+1));
                }else{
                    tmp[i] = tmp[i+1] = 'b';
                    que.push(pair<string, int> (tmp, num+1));
                }
            }
        }
    }

    return -1;
}

int main(void){
    cin >> worm;
    while(worm[0] != '0'){
        int result = solve();
        if(result >= 0){
            cout << result << endl;
        }else{
            cout << "NA" << endl;
        }
        cin >> worm;
    }

    return 0;
}

C++: #include<iostream>
#include<stdio.h>
#include<vector>
#include<stdlib.h>
#include<set>
#include<string>
#include<queue>
#include<map>

using namespace std;


int main(){



	string start_str;

	cin >> start_str;

	do{

		int ans = -1;

		queue< pair<int, string> > que;	//待ち行列 

		set<string> check_str;

		que.push(make_pair(0 , start_str));
		while (que.size()){

			string str;
			string sstr;	//色が変わったとき用

			int TIME = que.front().first;
			str = que.front().second;	//キューの先頭にある要素を取り出す
			que.pop();					//キューからポップする
			for (int i = 0; i < str.size() - 1; i++){
				if (str[i] != str[i + 1]){
					sstr = str;
					if (str[i] != 'r' && str[i + 1] != 'r'){
						sstr[i] = 'r'; sstr[i + 1] = 'r';
					}
					else if (str[i] != 'b' && str[i + 1] != 'b'){
						sstr[i] = 'b'; sstr[i + 1] = 'b';
					}
					else{
						sstr[i] = 'g'; sstr[i + 1] = 'g';
					}

					//cout << "TIME: " << TIME + 1 << "sstr: " << sstr << endl;

					if (sstr == start_str){	//変化した状態とスタートの状態が同じであったら
						continue;
					}
					else if (check_str.find(sstr) != check_str.end()){
						continue;
					}

					for (int j = 0; j < sstr.size() - 1; j++){
						if (sstr[j] != sstr[j + 1]){
							check_str.insert(sstr);
							que.push(make_pair(TIME + 1, sstr));	//make_pairは標準
							break;
						}

						if (j == sstr.size() - 2){	//一色に染まってたら
							ans = TIME + 1;
							i = str.size();
							while (!que.empty())
								que.pop();

						}

					}

				}
			}
		}

		if (ans == -1){
			for (int i = 0;i < start_str.size() - 1;i++){
				if (start_str[i] != start_str[i + 1]){
					cout << "NA" << endl;
					break;
				}

				if (i == start_str.size() - 2 ){
					cout << "0" << endl;
				}
			}
			
		}
		else{
			cout << ans << endl;
		}

		cin >> start_str;
	} while (start_str != "0");


	return 0;
}