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<cstdio>
#include<iostream>
#include<algorithm>
#define int long long
using namespace std;
int w,h,xs,ys,xg,yg,n,c,d,x,y,nok,sc;
int fld[101][101];
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
void dfs(int fx,int fy){
    if(fld[fy][fx]!=sc||fx<0||fx>w-1||fy<0||fy>h-1)return;
    fld[fy][fx]=0;
    for(int i=0;i<4;i++){
        dfs(fx+dx[i],fy+dy[i]);
    }
}
signed main(){
    for(;;){
        cin>>w>>h;
        if(w==0&&h==0)break;
        cin>>xs>>ys;
        cin>>xg>>yg;
        cin>>n;
        nok=0;
        fill(fld[0],fld[0]+101*101,-1);
        for(int i=0;i<n;i++){
            cin>>c>>d>>x>>y;
            x--,y--;
            if(d==0){
                for(int j=0;j<2;j++){
                    for(int k=0;k<4;k++){
                        fld[y+j][x+k]=c;
                    }
                }
            }
            if(d==1){
                for(int j=0;j<4;j++){
                    for(int k=0;k<2;k++){
                        fld[y+j][x+k]=c;
                    }
                }
            }
        }
        sc=fld[ys-1][xs-1];
       /* for(int j=0;j<h;j++){
            for(int k=0;k<w;k++){
                cout<<fld[j][k];
            }
            cout<<endl;
        }*/
        if(fld[0][0]!=-1){
            dfs(0,0);
        }
        /*for(int j=0;j<h;j++){
            for(int k=0;k<w;k++){
                cout<<fld[j][k];
            }
            cout<<endl;
        }*/
        if(fld[yg-1][xg-1]==0)cout<<"OK"<<endl;
        else cout<<"NG"<<endl;
    }
    return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int w,h,xs,ys,xg,yg,n,ban[101][101]={{0},{0}};
const int START=4545191;
const int GOAL=454545;
const int CHECKED=432535;

	bool dfs(int x,int y,int c){
		//cout<<x<<" "<<y<<endl;
		if(ban[x][y+1]==CHECKED&&ban[x+1][y]==CHECKED)return false;
		if(xg==x&&yg==y)return true;
		if(ban[x+1][y]==c){
			ban[x+1][y]=CHECKED;
			if(dfs(x+1,y,c))return true;
		}
		if(ban[x][y+1]==c){
			ban[x][y+1]=CHECKED;
			if(dfs(x,y+1,c))return true;
		}
		return false;
	}


int main(){

	while(cin>>w>>h&&w&&h){
	cin>>xs>>ys>>xg>>yg>>n;
	for(int i=0;i<101;i++)
	for(int j=0;j<101;j++)ban[i][j]=0;
	for(int i=0;i<n;i++){
		int c,d,x,y;
		cin>>c>>d>>x>>y;
		if(!d){
			for(int i=x;i<x+4;i++){
				for(int j=y;j<y+2;j++){
					ban[i][j]=c;
				}
			}
		}
		else{
		for(int i=x;i<x+2;i++){
				for(int j=y;j<y+4;j++){
					ban[i][j]=c;
				}
			}
		}
	}
	if(dfs(xs,ys,ban[xs][ys]))cout<<"OK"<<endl;
	else cout<<"NG"<<endl;
	
	return 0;
	}

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;
        int M;
        cin >> M;
        vector<vector<int> > d(W+1, vector<int>(H+1));
        vector<vector<int> > used(W+1, vector<int>(H+1));

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

using namespace std;

int w, h, xs, ys, xg, yg, n;
int field[1024][1024];
bool vis[1024][1024];

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}};

void rec(int x, int y, int c){
	
	if( vis[y][x] || x <= 0 || w < x || y <= 0 || h < y || field[y][x] != c )
		return;
	
	vis[y][x] = true;
	
	rec(x+1, y, c);
	rec(x-1, y, c);
	rec(x, y+1, c);
	rec(x, y-1, c);
	
	return;
}

int main()
{
	while(cin >> w >> h, (w||h)){
	
		memset(field,0,sizeof(field));
		memset(vis,0,sizeof(vis));
		
		cin >> xs >> ys;
		cin >> xg >> yg;
		
		cin >> n;
		
		for(int k = 0; k < n; ++k){
			
			int c, d, x, y;
			
			cin >> c >> d >> x >> y;
			
			for(int i = 0; i < 8; ++i){
				
				field[y+dy[d][i]][x+dx[d][i]] = c;
			}
		}
		
		
		rec(xs,ys,field[ys][xs]);
		
		cout << (vis[yg][xg]?"OK":"NG") << endl;
	
	}
	
	return 0;
}