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 <set>
#include <queue>
#include <map>

using namespace std;

int main(int argc, char const *argv[])
{
	string s,temp;
	int cnt;
	int i1,i2;
	int check;

	map<string,string> clr;
	clr["rg"]="bb";
	clr["gr"]="bb";
	clr["gb"]="rr";
	clr["bg"]="rr";
	clr["br"]="gg";
	clr["rb"]="gg";

	while(1){
		cin>>s;
		if(s=="0") break;

		queue<pair<string,int> > q;
		q.push(make_pair(s,0));
		set<string> bf;
		bf.insert(s);

		while(!q.empty()){
			s=q.front().first;
			cnt=q.front().second;
			q.pop();

			check=0;
			for(i1=0;i1<s.size()-1;i1++){
				if(s[i1]!=s[i1+1]) {
					check=1;
					if(i1<s.size()-2){
						temp=s.substr(0,i1)+clr[s.substr(i1,2)]+s.substr(i1+2);
					}
					else {
						temp=s.substr(0,i1)+clr[s.substr(i1,2)];
					}

					if(bf.find(temp)==bf.end()) {
						q.push(make_pair(temp,cnt+1));
						bf.insert(temp);
					}
				}
			}
			if(check==0) {
				check=2;
				break;
			}
		}

		if(check==2) cout<<cnt<<endl;
		else cout<<"NA"<<endl;
	}
	return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <map>
#include <queue>
#include <string>
using namespace std;

bool isSameColor(string a){
	char b=a[0];
	int s=a.size();
	
	for(int i=0; i<s; ++i){
		if(a[i]!=b) return false;
	}
	
	return true;	
}

int main(){
	string s;
	while(cin>>s){
		if(s=="0") break;
		
		queue<string> que;
		map<string, long> mp;
		
		que.push(s);
		mp[s]=0;	
		
		bool found=false;
		while(!que.empty()){
			string v=que.front();
			que.pop();
			
			int size=v.size();
			for(int i=0; i<size-1; ++i){
				string tmp=v;
				
				if((tmp[i]=='r'&&tmp[i+1]=='g') || (tmp[i]=='g'&&tmp[i+1]=='r')) tmp[i]=tmp[i+1]='b';
				else if((tmp[i]=='r'&&tmp[i+1]=='b') || (tmp[i]=='b'&&tmp[i+1]=='r')) tmp[i]=tmp[i+1]='g';
				else if((tmp[i]=='b'&&tmp[i+1]=='g') || (tmp[i]=='g'&&tmp[i+1]=='b')) tmp[i]=tmp[i+1]='r';
				
				if(mp.find(tmp) == mp.end()){
					que.push(tmp);
					mp[tmp]=mp[v]+1;	
				}
				
				if(isSameColor(tmp)){
					cout << mp[tmp] << endl;	
					found=true;
					break;
				}	
			}	
			
			if(found) break;
		}
		
		if(!found) printf("NA\n");
		
	}
}

C++: #include<cstdio>
#include<iostream>
#include<algorithm>
#include<queue>
#include<cmath>
using namespace std;
struct s{
    string worm;
    int nowans;
};
int main(){
    char dc[6][3]={'r','g','b','g','r','b','r','b','g','b','r','g','g','b','r','b','g','r'};
    while(1){
        int che[100000]={0},chenum=0;
        s IN,now;
        queue 
 que;
        cin >> IN.worm;
        IN.nowans=0;
        if(IN.worm[0]=='0')
            break;
        que.push(IN);
        while(1){
            chenum=0;
            now=que.front(),que.pop();
            for(int i=0;i<now.worm.size();i++){
                if(now.worm[i]=='r')
                    chenum+=pow(3,i);
                else if(now.worm[i]=='g')
                    chenum+=pow(3,i)*2;
                else if(now.worm[i]=='b')
                    chenum+=pow(3,i)*3;
            }
            if(che[chenum])
                continue;
            else
                che[chenum]=1;
            for(int i=0;i<now.worm.size()-1;i++){
                if(now.worm[i]!=now.worm[i+1])
                    break;
                if(i==now.worm.size()-1-1){
                    printf("%d\n",now.nowans);
                    goto exit;
                }
            }
            if(now.nowans==20){
                puts("NA");
                goto exit;
            }
            for(int i=0;i<now.worm.size()-1;i++){
                if(now.worm[i]!=now.worm[i+1]){
                    for(int j=0;j<6;j++){
                        if(now.worm[i]==dc[j][0]&&now.worm[i+1]==dc[j][1]){
                            now.worm[i]=dc[j][2],now.worm[i+1]=dc[j][2],now.nowans++;
                            que.push(now);
                            now.worm[i]=dc[j][0],now.worm[i+1]=dc[j][1],now.nowans--;
                        }
                    }
                }
            }
        }
exit:
    printf("");
    }
    return 0;
}