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 <cstdio>
#include <cstdlib>
#include <string>
#include <vector>
#include <deque>
#include <list>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <cstring>
#include <cctype>
#include <sstream>
#include <set>
#include <map>
#include <queue>
#include <complex>
using namespace std;

int main() {
  string musi;
  while(cin >> musi, musi != "0") {
    string tonum;
    for(int i=0; i<musi.size(); i++) {
      if(musi[i] == 'r')
        tonum.push_back('1');
      if(musi[i] == 'g')
        tonum.push_back('2');
      if(musi[i] == 'b')
        tonum.push_back('3');
    }
    queue< pair<string, int> > q;
    pair<string, int> p;
    p.first = tonum;
    p.second = 0;
    q.push(p);
    bool flg = true;
    vector<string> memo;
    while(q.size()) {
      p = q.front();
      q.pop();
      int cnt = 0;
      for(int i=1; i<p.first.size(); i++) {
        if(p.first[i-1] != p.first[i]) {
          pair<string, int> p2;
          p2 = p;
          int n = (int)p.first[i-1] + (int)p.first[i] - '0' - '0';
          if(n==3) {
            p2.first[i-1] = '3';
            p2.first[i] = '3';
          }
          else if(n==4) {
            p2.first[i-1] = '2';
            p2.first[i] = '2';
          }
          else if(n==5) {
            p2.first[i-1] = '1';
            p2.first[i] = '1';
          }
          if(find(memo.begin(), memo.end(), p2.first) == memo.end()) {
            p2.second++;
            q.push(p2);
            memo.push_back(p2.first);
          }
        }
        else cnt++;
      }
      if(cnt == p.first.size()-1) {
        flg = false;
        cout << p.second << endl;
        break;
      }
    }
    if(flg) cout << "NA" << endl;
  }
  return 0;
}

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

using namespace std;

typedef pair <string, int> P;

#define mp(a, b) make_pair(a, b)

char diff(char a, char b)
{
	if (a != 'r' && b != 'r') return 'r';
	if (a != 'g' && b != 'g') return 'g';
	if (a != 'b' && b != 'b') return 'b';
	return 'a';
}

bool check(string str)
{
	char c = str[0];
	for (int i = 0; i < str.length(); i++){
		if (c != str[i]) return false;
	}

	return true;
}

int main(void)
{
	string str;
	map <string, bool> memo;

	while (cin >> str){
		if (str == "0") return 0;

		int ret = -1, a;
		queue < P > q;
		q.push(mp(str, 0));
		while (!q.empty()){
			P now = q.front();
			q.pop();
			if (memo[now.first]){
				continue;
			}
			memo[now.first] = true;
			if (check(now.first)){
				ret = now.second;
				break;
			}
			for (int i = 0; i < now.first.length()-1; i++){
				if (now.first[i] != now.first[i + 1]){
					string tmp = now.first;
					tmp[i] = diff(now.first[i], now.first[i + 1]);
					tmp[i + 1] = diff(now.first[i], now.first[i + 1]);
					q.push(mp(tmp, now.second + 1));
				}
			}
		}

		if (ret >= 0) cout << ret << endl;
		else cout << "NA" << endl;
	}

	return 0;
}

C++: #include <stdio.h>
#include <string.h>


#define Q_MAX 1000000
#define N 11

typedef struct {
	int cost;
	char color[N];
} QUEUE;


int main(void)
{
	char bug[N];
	int i, j;
	static QUEUE que[Q_MAX];
	int sq, eq;
	static char used[Q_MAX][N];
	
	do {
		int count = -1;
		scanf("%s", bug);
		
		if (bug[0] == '0') break;
		
		sq = 0;
		eq = 1;
		memset(que, 0, sizeof(que));
		memset(used, 0, sizeof(used));
		que[sq].cost = 0;
		strcpy(que[sq].color, bug);
		
		while (sq != eq){
			char color[N];
			int cost = que[sq].cost;
			
			strcpy(color, que[sq].color);
			sq = (sq + 1) % Q_MAX;
			
			if (strncmp(color, "rrrrrrrrrr", strlen(color)) == 0 ||
			strncmp(color, "gggggggggg", strlen(color)) == 0 ||
			strncmp(color, "bbbbbbbbbb", strlen(color)) == 0){
				count = (cost);
				break;
			}
			
			for (i = 0; color[i + 1] != '\0'; i++){
				if (color[i] != color[i + 1]){
					char buf[N];
					char check[3] = {1, 1, 1};
					char flag = 1;
					
					strcpy(buf, color);
					if (buf[i] == 'r' || buf[i + 1] == 'r') check[0] = 0;
					if (buf[i] == 'g' || buf[i + 1] == 'g') check[1] = 0;
					if (buf[i] == 'b' || buf[i + 1] == 'b') check[2] = 0;
					
					if (check[0] == 1){
						buf[i] = 'r';
						buf[i + 1] = 'r';
					}
					if (check[1] == 1){
						buf[i] = 'g';
						buf[i + 1] = 'g';
					}
					if (check[2] == 1){
						buf[i] = 'b';
						buf[i + 1] = 'b';
					}
					
					
					if (flag == 1){
						que[eq].cost = cost + 1;
						strcpy(que[eq].color, buf);
						strcpy(used[eq], buf);
						eq = (eq + 1) % Q_MAX;
					}
				}
			}
		}
		if (count != -1){
			printf("%d\n", count);
		}
		else {
			printf("NA\n");
		}
		
	} while (1);
	
	return (0);
}