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<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<complex>
#include<cmath>
#include<algorithm>
#include<map>
#include<vector>
#include<sstream>
#include<iostream>
#include<queue>
using namespace std;
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
struct point{
    int x,y;
    point(){}
    point(int a, int b){x = a;y = b;}
};
int main(void){

    int w,h;
    while(cin>>w>>h,w){
        int xs,ys,xg,yg,n;
        cin>>xs>>ys>>xg>>yg>>n;
        int field[120][120] = {{0}};
        for(int i = 0;i < n;i++){
            int c,d,x,y;
            int dw = 4,dh = 2;
            cin>>c>>d>>x>>y;
            if(d)swap(dw,dh);
            for(int di = y;di < dh + y; di++){
                for(int dj = x;dj < dw + x;dj++){
                    field[di][dj] = c;
                }
            }
        }
        int C = field[xs][ys];
        bool vis[120][120] = {{false}};
        queue<point> Q;
        Q.push(point(xs,ys));
        if(field[xg][yg] != C || C == 0)cout<<"NG"<<endl;
        else {
            while(!Q.empty()){
                point P = Q.front();
                Q.pop();
                for(int i = 0;i < 4;i++){
                    point p = point(P.x + dx[i],P.y + dy[i]);
                    if(0 <= p.x && p.x < w && 0 <= p.y && p.y < h){
                        if(!vis[p.x][p.y]&&field[p.x][p.y] == C){

                            vis[p.x][p.y] = true;
                            Q.push(p);
                        }
                    }
                }
            }

        if(vis[xg][yg])cout<<"OK"<<endl;
        else cout<<"NG"<<endl;
        }
/*
        for(int i = 0;i < h;i++){
            for(int j = 0;j < w;j++){
                cout<<field[i][j]<<" ";
            }
            cout<<endl;
        }
        cout<<endl<<endl;
        for(int i = 0;i < h;i++){
            for(int j = 0;j < w;j++){
                cout<<vis[i][j]<<" ";
            }
            cout<<endl;
        }*/
        //cout<<C<<"---"<<field[xg][yg]<<endl;
    }


    return 0;
}

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

int F[102][102];
int xg,yg;
int flag = 0;

void DFS(int Y,int X,int c){
  if(F[Y][X] != c){
    return;
  }
  if(Y == xg && X == yg){
    flag = 1;
  }

  F[Y][X] = 0;
  DFS(Y-1,X  ,c);
  DFS(Y  ,X+1,c);
  DFS(Y+1,X  ,c);
  DFS(Y  ,X-1,c);
}


int main(){
  int w,h,xs,ys,n;
  while(1){
    cin >> w >> h;
    if(w == 0 && h == 0)
      break;

    cin >> xs >> ys >> xg >> yg >> n;
  
    for(int y=0; y<=h; y++){
      for(int x=0; x<=w; x++){
          F[y][x] = 0;
      }
    }
    for(int i=0;i<n;i++){
      int c,d,x,y;
      cin >> c >> d >> x >> y;
      if(d == 0){
        for(int j=0;j<4;j++){
          F[x+j][y] = c;
          F[x+j][y+1] = c;
        }
      } else {
        for(int j=0;j<4;j++){
          F[x][y+j] = c;
          F[x+1][y+j] = c;
        }
      }
    }

  DFS(xs,ys,F[xs][ys]);
  if(flag == 1){
    cout << "OK" << endl;
  } else {
    cout << "NG" <<endl;
  }
}
}

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

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pll> pip;
const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-9;

int dx[2][8] = {
	{ 0,1,2,3,0,1,2,3 },
	{ 0,1,0,1,0,1,0,1 }
};

int dy[2][8] = {
	{ 0,0,0,0,1,1,1,1 },
	{ 0,0,1,1,2,2,3,3 }
};

int main() {
	int w, h;
	while (cin >> w >> h, w || h) {
		int sx, sy, gx, gy;
		scanf("%d %d %d %d", &sx, &sy, &gx, &gy);
		sx--; sy--; gx--; gy--;
		
		int maps[100][100];
		memset(maps, -1, sizeof(maps));
		
		int n; cin >> n;
		
		REP(i, n) {
			int c, d, x, y;
			scanf("%d %d %d %d", &c, &d, &x, &y);
			x--; y--;
			
			REP(j, 8) {
				int xx = x + dx[d][j], yy = y + dy[d][j];
				maps[yy][xx] = c - 1;
			}
		}
		
		int num = maps[sy][sx];
		bool done[100][100] = {};
		
		queue<pii> que;
		if (num != -1) que.push(pii(sy, sx));
		done[sy][sx] = true;
		
		while (!que.empty()) {
			pii now = que.front(); que.pop();
			int x = now.se, y = now.fi;
			
			int ddx[4] = {1,0,-1,0}, ddy[4] = {0,1,0,-1};
			REP(i, 4) {
				int xx = x + ddx[i], yy = y + ddy[i];
				if (!(xx >= 0 && xx < w && yy >= 0 && yy < h)) continue;
				if (maps[yy][xx] != num || done[yy][xx]) continue;
				done[yy][xx] = true;
				que.push(pii(yy, xx));
			}
		}
		
		if (done[gy][gx] && num != -1) puts("OK");
		else puts("NG");
	}
	return 0;
}