Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

var (
	dx = []int{0, -1, 0, 1}
	dy = []int{1, 0, -1, 0}
)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		w, _ := strconv.Atoi(buf[0])
		h, _ := strconv.Atoi(buf[1])
		if w == 0 && h == 0 {
			break
		}
		scanner.Scan()
		buf_ := strings.Split(scanner.Text(), " ")
		xs, _ := strconv.Atoi(buf_[0])
		ys, _ := strconv.Atoi(buf_[1])
		scanner.Scan()
		buf__ := strings.Split(scanner.Text(), " ")
		xg, _ := strconv.Atoi(buf__[0])
		yg, _ := strconv.Atoi(buf__[1])
		xs--
		ys--
		xg--
		yg--
		scanner.Scan()
		n, _ := strconv.Atoi(scanner.Text())
		field := make([][]int, 100)
		for i := range  field {
			field[i] = make([]int, 100)
		}
		visited := make([][]bool, 100)
		for i := range visited {
			visited[i] = make([]bool, 100)
		}
		for i := 0; i < n; i++ {
			scanner.Scan()
			buf___ := strings.Split(scanner.Text(), " ")
			c, _ := strconv.Atoi(buf___[0])
			d, _ := strconv.Atoi(buf___[1])
			x, _ := strconv.Atoi(buf___[2])
			y, _ := strconv.Atoi(buf___[3])
			x--
			y--
			switch d {
			case 0:
				for j := 0; j < 4; j++ {
					for k := 0; k < 2; k++ {
						field[x+j][y+k] = c
					}
				}
			case 1:
				for j := 0; j < 2; j++ {
					for k := 0; k < 4; k++ {
						field[x+j][y+k] = c
					}
				}
			}
		}
		if field[xs][ys] != field[xg][yg] || // スタートとゴールの色が等しくないと"NG"
			field[xs][ys] == 0 { // スタートの色が無職
			fmt.Println("NG")
			continue
		}
		Q := make([]Entry, 0)
		visited[xs][ys] = true
		Q = append(Q, Entry{xs, ys})
		for len(Q) > 0 {
			row := Q[0].x
			col := Q[0].y
			Q = Q[1:]
			for i := 0; i < 4; i++ {
				if 0 <= row+dx[i] && row+dx[i] < w &&
					0 <= col+dy[i] && col+dy[i] < h && // 移動可能な範囲内かどうか
					!visited[row + dx[i]][col + dy[i]] && // 訪問済みか
					field[row+dx[i]][col+dy[i]]==field[row][col] { // 色が同じかどうか
						visited[row+dx[i]][col+dy[i]] = true
						Q = append(Q, Entry{row+dx[i],col+dy[i]})
				}
			}
		}
		if visited[xg][yg] {
			fmt.Println("OK")
		} else {
			fmt.Println("NG")
		}
	}
}

type Entry struct {
	x, y int
}

C++: #include<iostream>
#include<cstring>
#include<queue>
#include<map>
using namespace std;
int C,goal,n,x,y,xs,ys,xg,yg,mas[110][110]={{0}};
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,1};
int d[110][110];
typedef pair<int,int>P;

int bfs();
int main(){

  while(1){
    goal=0;
    memset(mas,0,sizeof(mas));
    //memset(d,0,sizeof(d));
    C = goal = n = x = y = xs = ys = xg = yg = 0;

    cin >> x >> y;//ボードの大きさ。 ※：x=横。y=縦。
    if(x==0 && y==0){
      break;
    }
    cin >> xs >> ys;//スタート地点。
    cin >> xg >> yg;//ゴール地点。
    cin >> n;//ブロックの数。
    
    //色染め。
    int color,dire,xx,yy;
    for(int t=0;t<n;t++){
      cin >> color >> dire >> xx >> yy;

      //横長。
      if(dire==0){
	for(int i=0;i<2;i++){
	  for(int j=0;j<4;j++){
	    mas[yy+i][xx+j]=color;
	  }
	}
      }
      
      //縦長。
      else{
	for(int i=0;i<4;i++){
	  for(int j=0;j<2;j++){
	    mas[yy+i][xx+j]=color;
	  }
	}
      }
      
    }
    
    //通る色　摘出。
    C=mas[ys][xs];
    //cout << "color:" << C << endl;
    
    if(C!=0 && mas[ys][xs]==mas[yg][xg]){

      bfs();

    
      if(goal==1){
	cout << "OK" << endl;
	goal=0;
      }
      else{
	cout << "NG" << endl;
      }
    }
    else{
      cout << "NG" << endl;
    }
  }
}

int bfs(){
  queue<P>que;
  memset(d,-1,sizeof(d));
  que.push(P(ys,xs));
  d[ys][xs]=0;
  while(!que.empty()){
    P p=que.front();
    que.pop();
    if(p.first==yg && p.second==xg){
      goal=1;
      break;
    }
    for(int i=0;i<4;i++){
      int ny=p.first+dy[i];
      int nx=p.second+dx[i];
      if(ny>=1 && ny<=y && nx>=1 && nx<=x && mas[ny][nx]==C && d[ny][nx]==-1){
	d[ny][nx] = 1;
	que.push(P(ny,nx));
      }
    }
  }
  return (0);
}

C++: #include <cstdio>
#include <cstring>
using namespace std;

int  map[100][100];
bool visited[100][100];
int  w,h;
int  xs,ys;
int  xg,yg;
int  n;

int dfs(int x,int y) {
	static int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
	if(x==xg&&y==yg) return 1;
	visited[x][y]=true;
	for(int i=0;i<4;i++) {
		int nx=x+dx[i],ny=y+dy[i];
		if(0<=nx&&nx<w&&0<=ny&&ny<h&&map[x][y]==map[nx][ny]&&!visited[nx][ny]) {
			if(dfs(nx,ny)) return 1;
		}
	}
	return 0;
}

int main() {
	int c,d,x,y;

	while(1) {
		memset(map,0,sizeof(map));
		memset(visited,0,sizeof(visited));
		scanf("%d %d",&w,&h);
		if(w==0&&h==0) break;
		scanf("%d %d",&xs,&ys);xs--;ys--;
		scanf("%d %d",&xg,&yg);xg--;yg--;
		scanf("%d",&n);
		for(int i=0;i<n;i++) {
			scanf("%d %d %d %d",&c,&d,&x,&y);x--;y--;
			int X,Y;
			if(d==1) {
				X=2;Y=4;
			}else {
				X=4;Y=2;
			}
			for(int j=0;j<X;j++) {
				for(int k=0;k<Y;k++) {
					map[x+j][y+k]=c;
				}
			}
		}
		printf("%s\n",dfs(xs,ys)?"OK":"NG");
	}
}

C++: #include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;

bool dfs(int x,int y,int color);
int w,h;
int xs,ys;
int xg,yg;
int board[111][111];
int cheak[111][111];
int xd[]={0,-1,0,1};
int yd[]={-1,0,1,0};
int main(){
  int n;
  int c,d,x,y;
  int a[]={1,0,1,0,1,0,1};
  int b[]={0,1,1,2,2,3,3};
  while(1){
    cin >> w >> h;
    if(w==0 && h==0) break;
    memset(board,0,sizeof(board));
    memset(cheak,0,sizeof(cheak));
    cin >> xs >> ys;
    cin >> xg >> yg;
    cin >> n;
    for(int i=0;i<n;i++){
      cin >> c >> d >> x >> y;
      board[y-1][x-1]=c;
      for(int j=0;j<7;j++){
	if(d==0) board[y+a[j]-1][x+b[j]-1]=c;
	else board[y+b[j]-1][x+a[j]-1]=c;
      }
    }
    if(board[ys][xs]!=0){
      if(dfs(xs-1,ys-1,board[ys-1][xs-1])==true) cout << "OK" << endl;
      else cout << "NG" << endl;
    }
    else cout << "NG" << endl;
  }
}

bool dfs(int x,int y,int color){
  board[y][x]=0;
  if(x==xg-1 && y==yg-1) return true;
  for(int i=0;i<4;i++){
    int xn=x+xd[i];
    int yn=y+yd[i];
    if(xn>=0 && xn<w && yn>=0 && yn<h && board[yn][xn]==color && board[yn][xn]!=0){
      if(dfs(xn,yn,board[yn][xn])==true) return true;
    }
  }
  return false;
}

C++: #include<iostream>
#include<vector>

using namespace std;

void PutBlock(vector< vector<int> >&, int, int, int, int);
void CheckMaze1(vector< vector<int> >&, int&, int, int, int, int, int);
void CheckMaze2(vector< vector<int> >&, int&, int, int, int, int, int);

int main(){
  int i, w, h, n, xs, ys, xg, yg, c, d, x, y, color, ans;
  vector<int> _data;
  vector< vector<int> > data;

  while(1){
    cin >> w >> h;
    if(w == 0 && h == 0) break;

    for(i=0; i<w; ++i)
      _data.push_back(0);

    for(i=0; i<h; ++i)
      data.push_back(_data);

    cin >> ys >> xs;
    cin >> yg >> xg;
    --xs;
    --xg;
    --ys;
    --yg;

    cin >> n;

    for(i=0; i<n; ++i){
      cin >> c >> d >> y >> x;
      PutBlock(data, c, d, x-1, y-1);
    }

    color = data[xs][ys];

    ans = 0;
    CheckMaze1(data, ans, color, xs, ys, xg, yg);

    if(ans == 1)
      cout << "OK" << endl;
    else
      cout << "NG" << endl;

    _data.clear();
    data.clear();
  }

  return 0;
}

void PutBlock(vector< vector<int> >& data, int c, int d, int x, int y){
  int i, j;
  if(d == 0){
    for(i=x; i<x+2; ++i){
      for(j=y; j<y+4; ++j)
	data[i][j] = c;
    }
  }else{
    for(i=x; i<x+4; ++i){
      for(j=y; j<y+2; ++j)
	data[i][j] = c;
    }
  }
}

void CheckMaze1(vector< vector<int> >& data, int& ans, int color, int x, int y, int xg, int yg){
  data[x][y] = -1;
  if(x == xg && y == yg) ans = 1;

  CheckMaze2(data, ans, color, x-1, y, xg, yg);
  CheckMaze2(data, ans, color, x, y-1, xg, yg);
  CheckMaze2(data, ans, color, x+1, y, xg, yg);
  CheckMaze2(data, ans, color, x, y+1, xg, yg);
}

void CheckMaze2(vector< vector<int> >& data, int& ans, int color, int x, int y, int xg, int yg){
  if(x > -1 && x < data.size() && y > -1 && y < data[0].size() && data[x][y] == color)
    CheckMaze1(data, ans, color, x, y, xg, yg);
}