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<vector>

int w, h;
int xs, ys, xg, yg;
int cs;

bool isOK = false;

void calc(int (&field)[101][101], int x, int y){

	field[x][y] = -1;

	if (x == xg&&y == yg)isOK = true;

	if (x < w - 1 && field[x + 1][y] == cs)calc(field, x + 1, y);
	if (x > 0 && field[x - 1][y] == cs)calc(field, x - 1, y);
	if (y < h - 1 && field[x][y + 1] == cs)calc(field, x, y + 1);
	if (y > 0 && field[x][y - 1] == cs)calc(field, x, y - 1);

}

int main(){

	while (std::cin >> w >> h){

		if (w == 0 && h == 0)break;

		std::cin >> xs >> ys >> xg >> yg;

		xs--, ys--, xg--, yg--;

		int n;
		std::cin >> n;

		int field[101][101];
		for (int i = 0; i < 100; i++){
			for (int j = 0; j < 100; j++){
				field[i][j] = 0;
			}
		}

		for (int i = 0; i < n; i++){
			int c, d, x, y;
			std::cin >> c >> d >> x >> y;

			x--, y--;

			if (d == 0){
				for (int j = y; j < y + 2; j++){
					for (int k = x; k < x + 4; k++){
						field[k][j] = c;
					}
				}
			}
			if (d == 1){
				for (int j = y; j < y + 4; j++){
					for (int k = x; k < x + 2; k++){
						field[k][j] = c;
					}
				}
			}
		}

		cs = field[xs][ys];

		calc(field, xs, ys);

		if (cs != 0 && isOK)std::cout << "OK" << std::endl;
		else std::cout << "NG" << std::endl;

		isOK = false;
	}
	return 0;
}

C++: #include <bits/stdc++.h>

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define MAX 101

using namespace std;

int field[MAX][MAX];
bool went[MAX][MAX];
int w, h;
int sx, sy, gx, gy;
int scol;
const int dx[] = {0,0,1,-1};
const int dy[] = {1,-1,0,0};

bool dfs(int x, int y) {
	if(field[y][x] == 0) return false;
	if(x == gx && y == gy) return true;
	int ncol = field[y][x];
	field[y][x] = 0;
	rep(i, 4) {
		int nx = x + dx[i];
		int ny = y + dy[i];
		if(0 < nx && nx <= w && 0 < ny && ny <= h && ncol == field[ny][nx]) {
			/*rep(j, h) {
				rep(k, w) cout << field[j][k] << " ";
				cout << endl;
			}*/
			if(dfs(nx, ny)) return true;
		}
	}
	return false;
}

int main() {
	while(cin >> w >> h, w || h) {
		memset(field, 0, sizeof(field));
		memset(went, false, sizeof(went));
		int n;
		cin >> sx >> sy >> gx >> gy;
		cin >> n;
		rep(i, n) {
			int c, d, x, y;
			cin >> c >> d >> x >> y;
			rep(i, (d ? 4 : 2)) rep(j, (d ? 2 : 4)) field[y + i][x + j] = c;
		}
		/*rep(j, h) {
			rep(k, w) cout << field[j][k] << " ";
			cout << endl;
		}*/
		if(dfs(sx, sy)) cout << "OK" << endl;
		else cout << "NG" << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int w, h;
int gx, gy;
int vx[] = {0, 1, 0, -1};
int vy[] = {1, 0, -1, 0};
int block[100][100];
bool check[100][100];
bool flag;

void dfs(int y, int x) {

  /*
  for(int i = 0; i < h; ++i) {
    for(int j = 0; j < w; ++j) {
      if(i == y && j == x) cout << 'P';
      else if(i == gy && j == gx) cout << 'G';
      else cout << block[i][j];
    }
    cout << endl;
  }
  cout << endl;
  */

  if(y == gy && x == gx) {
    
    flag = true;
    return;

  } else {
    
    for(int i = 0; i < 4; ++i) {
      
      int ny = y + vy[i];
      int nx = x + vx[i];
      
      if(ny >= 0 && ny < h && nx >= 0 && nx < w && !check[ny][nx] && block[ny][nx] && block[ny][nx] == block[y][x]) {
	
	check[ny][nx] = true;
	dfs(ny, nx);
	//check[ny][nx] = false;

      }

    }

  }

}

int main() {

  int sx, sy;
  int n;
  int c, d, x, y;

  while(cin >> w >> h) {

    if(w == 0 && h == 0) break;

    cin >> sx >> sy;
    cin >> gx >> gy;
    cin >> n;

    --sx;
    --sy;
    --gx;
    --gy;

    for(int i = 0; i < h; ++i) {
      for(int j = 0; j < w; ++j) {
	block[i][j] = 0;
	check[i][j] = false;
      }
    }

    for(int i = 0; i < n; ++i) {
	
	cin >> c >> d >> x >> y;

	--x;
	--y;
	
	int bw, bh;

	if(d) {
	  bw = 2;
	  bh = 4;
	} else {
	  bw = 4;
	  bh = 2;
	}

	for(int j = 0; j < bh; ++j) {
	  for(int k = 0; k < bw; ++k) {
	    block[y + j][x + k] = c;
	  }
	}

    }

    flag = false;
    check[sy][sx] = true;
    dfs(sy, sx);

    cout << (flag ? "OK" : "NG") << endl;

  }

}

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

int F[102][102];
int xg, yg;

bool DFS(int Y, int X, int C)
{
  if(Y == yg && X == xg)
    return true;
  if(F[Y][X]!=C)
    return false;

  F[Y][X] = 0;

  bool tmp = 0;
  tmp += DFS(Y-1, X, C);
  tmp += DFS(Y+1, X, C);
  tmp += DFS(Y, X-1, C);
  tmp += DFS(Y, X+1, C);
  return tmp;
}

int main()
{
  while(1){
    F[102][102] = {};

    int w, h;
    cin >> w >> h;

    if(w == 0 && h == 0)
      return 0;

    int xs, ys;
    cin >> xs >> ys;

    cin >> xg >> yg;

    int n;
    cin >> n;

    int c, d, x, y;
    for(int i=0; i<n; i++){
      cin >> c >> d >> x >> y;
      if(d == 0)
        for(int j=0; j<2; j++)
          for(int k=0; k<4; k++)
            F[y+j][x+k] = c;
      else
        for(int j=0; j<4; j++)
          for(int k=0; k<2; k++)
            F[y+j][x+k] = c;
    }

    bool res = DFS(ys, xs, F[ys][xs]);

    if(res)
      cout << "OK" << endl;
    else
      cout << "NG" << endl;
  }
}