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 <queue>
#include <map>
#define INF 100000000
using namespace std;
typedef pair<string,int>P;

int bfs(string worm){
  queue<P>que;
  map<string,int>d;
  que.push(P(worm,0));
  while(!que.empty()){
    P p = que.front(); 
    string str = p.first;
    que.pop();
    if(d[p.first])continue;

    bool flag = false;
    for(int i = 0 ; i < str.size()-1 ; i++ ) {
      if(str[i] != str[i+1]){
	flag = true;
	break;
      }
    }
    if(!flag)return p.second;
    d[p.first] = p.second;
    for(int i = 0 ; i < str.size()-1 ; i++ ){
      if(str[i]!=str[i+1]){
	char tmp;
	if(str[i] != 'r' && str[i+1] != 'r' ){
	  tmp = 'r';
	}else if(str[i] != 'g' && str[i+1] != 'g'){
	  tmp = 'g';
	}else {
	  tmp = 'b';
	}
	string next = str;
	next[i] = next[i+1] = tmp; 
	que.push(P(next,p.second+1));
      }
    }
  }
  return -1;
}

int main(){
  string worm;
  while(cin >> worm){
    if(worm[0] == '0')break;
    int res = bfs(worm);
    if(res>=0)cout << res << endl;
    else cout << "NA" <<endl;
  }
  return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;

int main(){
  while(true){
    string s;
    cin>>s;
    if(s=="0")break;
    string sr(s.size(),'r');
    string sg(s.size(),'g');
    string sb(s.size(),'b');
    map<string,int> mp;
    queue<string> q;
    q.push(s);
    mp[s]=0;
    int f=0;
    if(s==sr||s==sb||s==sg){
      cout<<0<<endl;
    }else{
      //for(int i=0;i<1e6;i++){
      while(!q.empty()){
        string x=q.front();
        q.pop();
        for(int j=0;j<s.size()-1;j++){
          string y=x;
          if(y[j]=='r'&&y[j+1]=='g'){
            y[j]='b';
            y[j+1]='b';
          }else if(y[j]=='b'&&y[j+1]=='g'){
            y[j]='r';
            y[j+1]='r';
          }else if(y[j]=='r'&&y[j+1]=='b'){
            y[j]='g';
            y[j+1]='g';
          }else if(y[j]=='g'&&y[j+1]=='b'){
            y[j]='r';
            y[j+1]='r';
          }else if(y[j]=='g'&&y[j+1]=='r'){
            y[j]='b';
            y[j+1]='b';
          }else if(y[j]=='b'&&y[j+1]=='r'){
            y[j]='g';
            y[j+1]='g';
          }
          //cout<<mp[x]+1<<" "<<y<<endl;
          if(y==sr||y==sb||y==sg){
            cout<<mp[x]+1<<endl;
            f=1;
            break;
          }
          if(mp[y]==0){
            mp[y]=mp[x]+1;
            q.push(y);
          }
        }
        if(f)break;
      }
      if(!f)cout<<"NA"<<endl;
    }
  }
}

C++: #include<bits/stdc++.h>
using namespace std;
char c[3]={'r','g','b'};
main(){
  string w;
  while(cin>>w,w[0]!='0'){
    set<string>a;
    a.insert(w);
    queue<pair<string,int> >q;
    q.push(make_pair(w,0));
    while(!q.empty()){
      pair<string,int>ww=q.front();q.pop();
      string s=ww.first;//cout<<s<<endl;
      int d=ww.second;//cout<<d<<endl;
      int cc=0;
      for(int i=0;i<s.size()-1;i++)if(s[i]!=s[i+1])cc++;
      if(!cc){cout<<d<<endl;goto L;}
      for(int i=0;i<s.size()-1;i++){
        if(s[i]!=s[i+1]){
          int p=0;
          for(int k=0;k<3;k++)
            for(int j=0;j<3;j++)
              if(s[i]==c[k]&&s[i+1]==c[j])p=k+j;
          string t=s;
          if(p==3)t[i+1]=t[i]='r';
          else if(p==2)t[i+1]=t[i]='g';
          else t[i+1]=t[i]='b';
          if(!a.count(t)){//cout<<t<<endl;
            q.push(make_pair(t,d+1));
            a.insert(t);
          }
        }
      }
    }
    cout<<"NA"<<endl;
    L:;
  }
}