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 <string>
#include <queue>
using namespace std;

string insect = "brg";
int cnt;
queue <string> Q;
queue <string> Q2;

bool bfs( string str) {
  if ( cnt == 0 ) Q.push( str );
  while ( !Q2.empty() ) {
    string tmp;
    tmp = Q2.front();Q2.pop();
    Q.push(tmp);
  }
  
  int count = 0;
  while ( !Q.empty() ) {
    int flag = 0;
    count++;
    str = Q.front();
    Q.pop();
    string str2;
    int len = str.size();
    for ( int k = 0; k < len-1; k++ ) {
      if ( str[k] != str[k+1] ) flag = 1;
    }
    if ( flag == 0 ) return 1;
    for ( int i = 0; i < len-1; i++ ) {
      str2 = str;
      for ( int j = 0; j < 3; j++ ) {
	if ( str2[i] != str2[i+1] 
	     && str2[i] != insect[j] && str2[i+1] != insect[j] ) {
	  str2[i] = insect[j];
	  str2[i+1] = insect[j];
	  Q2.push( str2 );
	}
      }
    }
  }
  return 0;
}

int main() {

  while (1) {

    string str; cin >> str;
    if ( str == "0" ) break;
    while( !Q.empty() ) Q.pop();
    while( !Q2.empty() ) Q2.pop();
    cnt = -1;

    while (1) {
      cnt++;
      if ( cnt == 10 ){
	cout << "NA" << endl;
	break;
      }
      if ( bfs( str ) ) {
	cout << "ans" << " " << cnt << endl;
	break;
      }
    }

  }
  return 0;
}

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

using namespace std;

typedef pair<string, int> P;

//????????????????????????????????????
bool judge(string str) {
	for (int i = 0; i < str.size(); ++i) {
		if (str[0] != str[i]) return false;
	}
	return true;
}

//??£?????????2?????????????????§?????????????????????
char color(char a, char b){
	if((a == 'g' && b == 'r') || (a == 'r' && b == 'g'))return 'b';
	else if((a == 'b' && b == 'r') || (a == 'r' && b == 'b')) return 'g';
	else if((a == 'g' && b == 'b') || (a == 'b' && b == 'g')) return 'r';
}

int solve(string s ){

	queue<P> q;
	map<string, int> m;
	q.push(P(s, 0));	//?????\??????????????¶????????\??????
	if(m[p.first]) continue;	//??????????????????

	while (!q.empty()) {	//?????\??????????????¶?????????????????§
		P p = q.front();
		q.pop();
		string now = p.first;
		if (judge(now)) return p.second;
		for (int i = 0; i < now.size() - 1; ++i) {
			if (now[i] != now[i+1]){	//??£?????????2????????°????????¨???
				char tmp = color(now[i], now[i + 1]);
				string D = now;
				D[i] = tmp;
				D[i + 1] = tmp;
				q.push(P(D, p.second + 1));
			}
		}
	}
	return -1;
}

int main() {
	string worm;
	while (cin >> worm) {
		if (worm == "0") break;
		int count = solve(worm);
		if (count == -1) cout << "NA" << endl;
		else cout << count << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <queue>
#include <map>

using namespace std;
typedef pair<string, int> P;

void solve()
{
	string str;
	while(cin >> str)
	{
		if(str == "0")
		{
			break;
		}
		bool flag = true;
		for(int j = 0; j < str.size() - 1; ++j)
		{
			if(str[j] != str[j + 1])
			{
				flag = false;
				break;
			}
		}
		if(flag)
		{
			cout << 0 << endl;
			continue;
		}
		queue<P> Que;
		Que.push(make_pair(str, 0));
		queue<P> NextQue;
		map<string, int> Map;
		int step = 0;
		while(true)
		{
			if(step == str.size())
			{
				cout << "NA" << endl;
				break;
			}
			while(!Que.empty())
			{
				for(int i = 0; i < str.size() - 1; ++i)
				{
					string body = Que.front().first;
					if(body[i] == 'b' && body[i + 1] == 'g')
					{
						body[i] = body[i + 1] = 'r';
					}
					else if(body[i] == 'b' && body[i + 1] == 'r')
					{
						body[i] = body[i + 1] = 'g';
					}
					else if(body[i] == 'g' && body[i + 1] == 'b')
					{
						body[i] = body[i + 1] = 'r';
					}
					else if(body[i] == 'g' && body[i + 1] == 'r')
					{
						body[i] = body[i + 1] = 'b';
					}
					else if(body[i] == 'r' && body[i + 1] == 'b')
					{
						body[i] = body[i + 1] = 'g';
					}
					else if(body[i] == 'r' && body[i + 1] == 'g')
					{
						body[i] = body[i + 1] = 'b';
					}
					bool flag = true;
					for(int j = 0; j < str.size() - 1; ++j)
					{
						if(body[j] != body[j + 1])
						{
							flag = false;
							break;
						}
					}
					if(flag)
					{
						cout << Que.front().second + 1 << endl;
						goto NEXT;
					}
					if(!Map[body])
					{
						NextQue.push(make_pair(body, Que.front().second + 1));
					}
					Map[body]++;
				}
				Que.pop();
			}
			while(!NextQue.empty())
			{
				Que.push(NextQue.front());
				NextQue.pop();
			}
			++step;
		}
NEXT:
		;
	}
}

int main()
{
	solve();
	return(0);
}