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<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
int que[60000][10],flg[1050000];
int main(void){
	int p1,p2,i,j,len,time[60000],copy[10],f,x,ans,iro;
	char ca[11];
	while(1){
		cin>>ca;
		if(ca[0]=='0') break;
		len=strlen(ca);
		for(i=0;i<len;i++){
			if(ca[i]=='r') que[0][i]=0;
			if(ca[i]=='g') que[0][i]=1;
			if(ca[i]=='b') que[0][i]=2;
		}
		for(i=0;i<=1050000;i++) flg[i]=0;
		p1=0; p2=1; time[0]=0; ans=-1;
		while(1){
			if(p1==p2){
//				cout<<p1<<endl;
				break;
			}
/*			cout<<p1<<' ';
			for(i=0;i<len;i++) cout<<que[p1][i];
			cout<<' '<<time[p1]<<endl;*/
			f=1;
			for(i=0;i<len-1;i++){
				if(que[p1][i]!=que[p1][i+1]){
					f=0;
					break;
				}
			}
			if(f==1){
				ans=time[p1];
				break;
			}
			for(i=0;i<len-1;i++){
				for(j=0;j<len;j++) copy[j]=que[p1][j];
				if(copy[i]!=copy[i+1]){
					iro=copy[i]+copy[i+1];
					if(iro==3){
						copy[i]=0; copy[i+1]=0;
					}
					if(iro==2){
						copy[i]=1; copy[i+1]=1;
					}
					if(iro==1){
						copy[i]=2; copy[i+1]=2;
					}
				}
				x=copy[0];
				for(j=1;j<len;j++) x=x*4+copy[j];
				if(flg[x]==0){
					flg[x]=1; time[p2]=time[p1]+1;
					for(j=0;j<len;j++) que[p2][j]=copy[j];
					p2++;
				}
			}
			p1++;
		}
		if(ans==-1) cout<<"NA"<<endl;
		else cout<<ans<<endl;
	}
	return 0;
}

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;
    int test = 0;
    while(q.size()) {
      p = q.front();
      q.pop();
//      cout << p.first << ' ' << test << endl;
      test++;
      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(test > 100000) break;
      }
      if(cnt == p.first.size()-1) {
        flg = false;
        cout << p.second << endl;
        break;
      }
    }
    if(flg) cout << "NA" << endl;
  }
  return 0;
}