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>
using namespace std;
int n,w,h;
int M[101][101];
int a,b,c,d;

int walk(int x,int y,int color){
	if(x<1||w<x||y<1||h<y)return 0;
	if(color!=M[x][y]||color==0)return 0;
	M[x][y]=9;
	walk(x+1,y,color);
	walk(x-1,y,color);
	walk(x,y+1,color);
	walk(x,y-1,color);
	return 0;
}
int main(void){
	while(cin>>w>>h,w||h){
		cin>>a>>b>>c>>d;
		for(int i=1;i<=h;i++){
			for(int j=1;j<=w;j++){
				M[i][j]=0;
			}
		}
		int k;
		cin>>k;
		for(int i=0;i<k;i++){
			int w,x,y,z;
			cin>>w>>x>>y>>z;
			if(x){
				for(int Y=z;Y<z+4;Y++){
					for(int X=y;X<y+2;X++){
						M[Y][X]=w;
					}
				}
			}else{
				for(int Y=z;Y<z+2;Y++){
					for(int X=y;X<y+4;X++){
						M[Y][X]=w;
					}
				}
			}
		}
		walk(a,b,M[a][b]);
		if(M[c][d]==9)cout<<"OK"<<endl;
		else cout<<"NG"<<endl;
	}
	return 0;
}

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

typedef pair<int,int> P;

int main(){
  int w,h;
  int xs,ys,xg,yg;
  int n;
  int c,d,x,y;
  int grid[101][101];
  bool visit[101][101];

  for(;;){
    cin >> w >> h;
    if(!w && !h)break;

    for(int i=1;i<=h;i++)
      for(int j=1;j<=w;j++){
	grid[i][j] = 0;
	visit[i][j] = false;
      }
    cin >> xs >> ys >> xg >> yg;

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

    int color = grid[ys][xs];    
    queue<P> q;
    if(color){
      q.push(P(ys,xs));
      visit[ys][xs] = true;
      while(q.size()){
	P p = q.front();q.pop();
	y = p.first;
	x = p.second;
	
	int dx[] = {0,1,0,-1},dy[] = {-1,0,1,0};
	for(int i=0;i<4;i++){
	  int sx = x+dx[i],sy = y+dy[i];
	  if(sx<=0 || sy<=0 || w<=sx || h<=sy)continue;
	  if(visit[sy][sx] || grid[sy][sx]!=color)continue;
	  q.push(P(sy,sx));
	  visit[sy][sx] = true;
	}
      }
      if(visit[yg][xg])cout << "OK\n";
      else cout << "NG\n";
    }else{
      cout << "NG\n";
    }
  }
}

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

int main() {
    int H, W;
    while (cin >> W >> H, H || W) {
        int sx, sy, gx, gy;
        cin >> sx >> sy >> gx >> gy;
        // sx--, sy--, gx--, gy--;
        int M;
        cin >> M;
        vector<vector<int> > d(H+1, vector<int>(W+1));
        vector<vector<int> > used(H+1, vector<int>(W+1));

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

        int dx[] = {0, 1, 0, -1};
        int dy[] = {1, 0, -1, 0};

        queue<int> qx, qy;
        qx.push(sx);
        qy.push(sy);

        while (qx.size()) {
            int x = qx.front(); qx.pop();
            int y = qy.front(); qy.pop();

            if (used[x][y]) continue;
            used[x][y] = 1;

            for (int i = 0; i < 4; i++) {
                int nx = x + dx[i];
                int ny = y + dy[i];

                if (0 <= nx && nx <= H && 0 <= ny && ny <= W && !used[nx][ny] && d[x][y] == d[nx][ny]) {
                    qx.push(nx);
                    qy.push(ny);
                }
            }
        }

        if (used[gx][gy]) cout << "OK" << endl;
        else cout << "NG" << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <cstdio>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<(n);i++)
int dy[] = {1, 0, 0, -1};
int dx[] = {0, 1, -1, 0};
int b[110][110];
int w, h;
int xs, ys, xg, yg;
int color;
bool flag = false;
bool used[110][110];

void dfs(int y, int x, int py, int px){
	rep(i, 4){
		int ny = y + dy[i], nx = x + dx[i];
		if(used[ny][nx]) continue;//???????????¨???????????????????????????
		if(!(0 <= ny && ny < h && 0 <= nx && nx < w)) continue;
		if(b[ny][nx] != color) continue;
		if(ny == py && nx == px) continue;
		if(ny == yg && nx == xg){
			used[ny][nx] = true;
			flag = true; return;//????????????
		}
		used[ny][nx] = true;
		dfs(ny, nx, y, x);
	}
	return;//????????¢?????¨???????????????
}

int main(void){
	while(1){
		rep(i, 110)rep(j, 110){
			b[i][j] = -1; used[i][j] = false;
		}
		cin >> w >> h;
		if(w == 0 && h == 0) return 0;
		cin >> xs >> ys >> xg >> yg;
		xs--; ys--; xg--; yg--;
		int n; cin >> n;
		rep(i, n){
			int c, d, x, y;
			cin >> c >> d >> x >> y;
			x--; y--;
			if(d == 0){//?¨?
				b[y][x] = b[y][x + 1] = b[y][x + 2] = b[y][x + 3] = c;
				b[y + 1][x] = b[y + 1][x + 1] = b[y + 1][x + 2] = b[y + 1][x + 3] = c;
			}else{//???
				b[y][x] = b[y][x + 1] = c;
				b[y + 1][x] = b[y + 1][x + 1] = c;
				b[y + 2][x] = b[y + 2][x + 1] = c;
				b[y + 3][x] = b[y + 3][x + 1] = c;
			}
		}
		color = b[ys][xs];
		if(color == -1) {//?????????????????????????????????
			printf("NG\n"); continue;
		}
		used[ys][xs] = true;
		dfs(ys, xs, -1, -1);
		if(flag) printf("OK\n");
		else printf("NG\n");
	}
}