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 B[102][102];
bool maze = false;

void DFS(int Y, int X, int YG, int XG, int C)
{
  if(B[Y][X]!=C || C==0)
    return;

  if(Y==YG && X==XG)
    maze = true;

  B[Y][X] = 0;

  DFS(Y-1, X  , YG, XG, C);
  DFS(Y  , X+1, YG, XG, C);
  DFS(Y+1, X  , YG, XG, C);
  DFS(Y  , X-1, YG, XG, C);
}

int main()
{
  while(true){
    int w, h;
    cin >> w >> h;

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

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

    for(int y=0; y<=h; y++){
      for(int x=0; x<=w; x++){
	B[y][x] = 0;
      }
    }

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

    maze = false;

    DFS(ys, xs, yg, xg, B[ys][xs]);

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

  return 0;
}

C++: #include <iostream>
#include <queue>
#include <utility>
#define rep2(x,from,to) for(int x=(from);(x)<(to);(x)++)
#define rep(x,to) rep2(x,0,to)
#define pint pair<int,int>
using namespace std;
int main(){
	int dx[4] = {-1,0,1,0};
	int dy[4] = {0,1,0,-1};
	int w,h,xs,ys,xg,yg,n;
	while(cin >> w >> h && (w || h)) {
		cin >> xs >> ys >> xg >> yg >> n;
		int b[110][110] = {};
		int	c,d,x,y;
		rep(i,n) {
			cin >> c >> d >> x >> y;
			rep(j,2) {
				rep(k,4) {
					if(d==0) b[y+j][x+k] = c;
					else b[y+k][x+j] = c;
				}
			}
		}
		if(b[ys][xs] != b[yg][xg] || b[ys][xs] == 0) {
			cout << "NG" << endl;
			continue;
		}
		queue<pint> q;
		pint p;
		p.first = ys, p.second = xs;
		q.push(p);
		const int b_color = b[ys][xs];
		bool f = 0;
		while(!q.empty()) {
			pint a = q.front(); q.pop();
			b[a.first][a.second] = 0;
			if(a.first == yg && a.second == xg) {
				f = 1;
				break;
			}
			rep(i,4) {
				if(b[a.first+dy[i]][a.second+dx[i]] == b_color) {
					pint e;
					e.first = a.first+dy[i], e.second = a.second+dx[i];
					q.push(e);
				}
			}
		}
		if(f) cout << "OK" << endl;
		else cout << "NG" << endl;
	}
}

C++: #include <iostream>
#include <vector>

using namespace std;

#define repeat(n, i) for(int i=0; i<(n); i++)
int w, h;
int xs, ys;
int xg, yg;
int n;

int st_color;

int board[300][300];

#define VISITED 6

bool get_input() {
    cin >> w >> h;
    if (w == 0 && h == 0) return false;
//    board.resize(h);
//    repeat(h, i) board[i].resize(w);
    cin >> xs >> ys;
    cin >> xg >> yg;
    cin >> n;
    repeat(n, i) {
        int c, d, x, y;
        cin >> c >> d >> x >> y;
        if (d == 0) {
            for (int j = y-1; j < y-1+4; j++) {
                for (int k = x-1; k < x-1+2; k++) {
                    board[j][k] = c;
                }
            }
        } else {
            for (int j = y-1; j < y-1+2; j++) {
                for (int k = x-1; k < x-1+4; k++) {
                    board[j][k] = c;
                }
            }
        }
    }
    st_color = board[ys-1][xs-1];
    return true;
}

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

bool possible;
void dfs(int x, int y) {
    board[y-1][x-1] = VISITED;
    if (x == xg && y == yg) {
        possible = true;
        return;
    }
    repeat(4, i) {
        int nx = x+dx[i], ny = y+dy[i];
        if (1 <= nx && nx <= w && 1 <= ny && ny <= h) {
            if (board[ny-1][nx-1] != VISITED) {
                dfs(nx, ny);
            }
        }
    }
}

void solve() {
    possible = false; dfs(xs, ys);
    if (possible) cout << "OK" << endl;
    else cout << "NG" << endl;
}

int main() {
    while (get_input()) {
        solve();
    }
    return 0;
}

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

int f[102][102];

void DFS(int x,int y,int c){
    if(f[x][y]!=c)  return;

    f[x][y]=10;
    DFS(x+1,y,c);
    DFS(x-1,y,c);
    DFS(x,y+1,c);
    DFS(x,y-1,c);
}

int main(){
    int w,h;
    int xs,ys;
    int xg,yg;
    int n;
    while(true){
        cin>>w>>h;
        if(w+h==0)  break;
        for(int i=1;i<=w;i++){
            for(int j=1;j<=h;j++){
                f[i][j]=-1;
            }
        }
        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;
            if(d==1){
                for(int j = 0; j<4; j++){
                    for(int k = 0; k<2; k++){
                        f[x+j][y+k] = c;
                    }
                }
            }else{
                for(int j = 0; j<2; j++){
                    for(int k = 0; k<4; k++){
                        f[x+j][y+k] = c;
                    }
                }
            }
        }
        DFS(xs,ys,f[xs][ys]);
        if(f[xg][yg]==10){
            cout<<"OK"<<endl;
        }else{
            cout<<"NG"<<endl;
        }
    }
    return 0;
}