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++: // 2011/01/14 Tazoe

#include<iostream>
using namespace std;

bool DFS(int brd[102][102], int x, int y, int col, int xg, int yg)
{
	if(brd[y][x]!=col)
		return false;
	if(x==xg&&y==yg)
		return true;

	brd[y][x] = 9;

	return(DFS(brd, x+1, y, col, xg, yg)
	     ||DFS(brd, x, y+1, col, xg, yg)
	     ||DFS(brd, x-1, y, col, xg, yg)
	     ||DFS(brd, x, y-1, col, xg, yg));
}

int main()
{
	while(true){
		int w, h;
		cin >> w >> h;
		if(w==0&&h==0)
			break;

		int brd[102][102];
		for(int yy=0; yy<h+2; yy++)
			for(int xx=0; xx<w+2; xx++)
				brd[yy][xx] = 0;

		int xs, ys, xg, yg, n;
		cin >> xs >> ys;
		cin >> xg >> yg;
		cin >> n;

		for(int i=0; i<n; i++){
			int c, d, x, y;
			cin >> c >> d >> x >> y;
			brd[y  ][x  ] = c;
			brd[y  ][x+1] = c;
			brd[y+1][x  ] = c;
			brd[y+1][x+1] = c;
			if(d==0){
				brd[y  ][x+2] = c;
				brd[y  ][x+3] = c;
				brd[y+1][x+2] = c;
				brd[y+1][x+3] = c;
			}
			else{
				brd[y+2][x  ] = c;
				brd[y+2][x+1] = c;
				brd[y+3][x  ] = c;
				brd[y+3][x+1] = c;
			}
		}

		if(brd[ys][xs]==0||brd[yg][xg]==0||brd[ys][xs]!=brd[yg][xg]){
			cout << "NG" << endl;
			continue;
		}

		if(DFS(brd, xs, ys, brd[ys][xs], xg, yg))
			cout << "OK" << endl;
		else
			cout << "NG" << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <utility>
#include <numeric>
#include <algorithm>
#include <functional>
#include <cctype>
#include <complex>
#include <string>
#include <sstream>

using namespace std;

#define all(c) c.begin(),c.end()
#define rall(c) c.rbegin(),c.rend()
#define mp(a,b) make_pair((a),(b))
#define eq ==

typedef long long ll;
typedef complex<double> point;
typedef pair<int,int> pii;

// →↑←↓
const int dx[] = {1,0,-1,0};
const int dy[] = {0,-1,0,1};


const double EPS = 1e-9;

int main(){

    while(true){
        int w,h;
        cin >> w >> h;
        if(w == 0) break;
        int sy,sx,gy,gx;
        cin >> sx >> sy >> gx >> gy;
        sx--,sy--,gx--,gy--;
        int n;
        cin >> n;
        vector<vector<int> > color(h,vector<int>(w));
        for(int block=0;block<n;block++){
            int c,d,x,y;
            cin >> c >> d >> x >> y;
            x--;y--;
            // yoko
            if(d == 0){
                for(int i=0;i<2;i++){
                    for(int j=0;j<4;j++){
                        color[y+i][x+j] = c;
                    }
                }
            }else{
                for(int i=0;i<4;i++){
                    for(int j=0;j<2;j++){
                        color[y+i][x+j] = c;
                    }
                }
            }
        }
        // for(int i=0;i<h;i++){
        //     for(int j=0;j<w;j++){
        //         cerr << color[i][j];
        //     }
        //     cerr << endl;
        // }
        int c = color[sy][sx];
        vector<vector<char> > visited(h,vector<char>(w));
        queue<pair<int,int> > Q;
        Q.push(make_pair(sy,sx));
        while(not Q.empty()){
            int y = Q.front().first;
            int x = Q.front().second;
            Q.pop();

            if(y >= h or y < 0 or x >= w or x < 0) continue;
            if(color[y][x] != c) continue;
            if(visited[y][x]) continue;
            visited[y][x] = true;
            for(int i=0;i<4;i++){
                Q.push(make_pair(y+dy[i],x+dx[i]));
            }
        }
        if(visited[gy][gx]){
            cout << "OK" << endl;
        }else{
            cout << "NG" << endl;
        }
    }
    return 0;
}

C++: #include <iostream>
using namespace std;
#define MAX 100
 
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
 
int w, h, xs, ys, xg, yg, G[MAX+2][MAX+2];
 
bool dfs(int x, int y, int color){
    if(color == 0 || G[x][y] != color) return false;
    if(x==xg&&y==yg) return true;
    G[x][y] = 0;
    for(int r=0; r<4; r++){
        if(dfs(x+dx[r], y+dy[r], color)) return true;
    }
    return false;
}
 
int main(void)
{
    int n, c, d, bx, by;
    while(cin>>w>>h, w&&h){
        for(int x=0; x<w+2; x++){
            for(int y=0; y<h+2; y++){
                G[x][y] = 0;
            }
        }
        cin >> xs >> ys >> xg >> yg >> n;
        for(int i=0; i<n; i++){
            cin >> c >> d >> bx >> by;
            for(int i=0; i<4; i++){
                for(int j=0; j<2; j++){
                    if(d==0) G[bx+i][by+j] = c; 
                    else G[bx+j][by+i] = c;
                }
            }
        }
        if(dfs(xs, ys, G[xs][ys])) cout << "OK" << endl;
        else cout << "NG" << endl;
    }
    return 0;
}