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>
#include<cmath>
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){
			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+=2){
				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 <vector>
#include <algorithm>
#include <string>
#include <map>

using namespace std;

map<string,bool > passed;

const int INF=100000000;

int dfs(string str){
	if(passed.find(str)!=passed.end()&&passed[str]){
		return INF;
	}
	char cl=str[0];
	bool f=false;
	for(int i = 1; i < str.size(); i++){
		if(str[i]!=cl){
			f=true;
			break;
		}
	}
	if(!f)
		return 0;

	bool flag[200];
	int minCnt=INF;
	for(int i = 0; i < str.size()-1; i++){
		flag['r']=false;
		flag['g']=false;
		flag['b']=false;
		if(str[i]!=str[i+1]){
			flag[str[i]]=true;
			flag[str[i+1]]=true;
			if(!flag['r']){
				string nstr=str;
				nstr[i]='r';
				nstr[i+1]='r';
				passed[str]=true;
				minCnt=min(minCnt,dfs(nstr)+1);
				passed[str]=false;
			}
			else if(!flag['g']){
				string nstr=str;
				nstr[i]='g';
				nstr[i+1]='g';
				passed[str]=true;
				minCnt=min(minCnt,dfs(nstr)+1);
				passed[str]=false;
			}
			else if(!flag['b']){
				string nstr=str;
				nstr[i]='b';
				nstr[i+1]='b';
				passed[str]=true;
				minCnt=min(minCnt,dfs(nstr)+1);
				passed[str]=false;
			}
		}
	}
	return minCnt;
}

int main(){

	string str;
	while(cin>>str&&str!="0"){
		cout<<dfs(str)<<endl;
	}


	return 0;
}

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

int cnt,ccnt = 0;
int len;
string s, ss, tmp;
int flag = 0;
int fflag=0;
char c;
int cc=0;
vector<string> v_list;
pair<string,int> ps;
int main() {
	while (cin >> s) {
		if (s == "0") {
			break;
		}
		map<string,int> m;
		fflag=0;
		//v_list.push_back(s);
		len = s.length();
		queue<pair<string,int> > qq;
		qq.push(make_pair(s,0));
		while (!qq.empty()) {
			ps = qq.front();
			qq.pop();
			c = ps.first[0];
			ccnt=ps.second;
			flag = 0;

			for (int i = 1; i < len; i++) {
				if (c != ps.first[i]) {
					//cout<<ps.first[i]<<endl;//deb
					flag = 1;
					cc=i;
					break;
				}
			}
			if (flag) {
				for (int i = cc-1; i < len - 1; ++i) {
					tmp = ps.first;
					if (ps.first[i] != ps.first[i+1]) {
						if (ps.first[i] != 'r' && ps.first[i+1] != 'r') {
							tmp[i] = 'r';
							tmp[i + 1] = 'r';
							if(m[tmp])continue;
							m[tmp]=ps.second;
							qq.push(make_pair(tmp,ccnt+1));
						}
						if (ps.first[i] != 'g' && ps.first[i+1] != 'g' ){
							tmp[i] = 'g';
							tmp[i + 1] = 'g';
							if(m[tmp])continue;
							m[tmp]=ps.second;
							qq.push(make_pair(tmp,ccnt+1));
						}
						if (ps.first[i] != 'b' && ps.first[i+1] != 'b') {
							tmp[i] = 'b';
							tmp[i + 1] = 'b';
							if(m[tmp])continue;
							m[tmp]=ps.second;
							qq.push(make_pair(tmp,ccnt+1));
						}
					}
				}
			} else {
				cout << ccnt << endl;
				fflag=1;
				break;
			}
		}
		if(!fflag){printf("NA");cout<<endl;};
	}
	return 0;
}