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>
#include<algorithm>
#include<string>
using namespace std;
int w,h,xs,ys,xg,yg,n,ban[111][111]={{0},{0}};
bool visited [101][101];
const int START=4545191;
const int GOAL=454545;

	bool dfs(int x,int y){
		//cout<<x<<" "<<y<<endl;
		if(xg==x&&yg==y)return true;
		if(x==xs&&ys==y&&ban[x][y]==-1)return false;
		//if(ban[xs][ys]==0)return false;
		if(ban[x+1][y]==ban[xs][ys]&&visited[x][y]==false){
			visited[x][y]=true;
			if(dfs(x+1,y))return true;
		}
		if(ban[x][y+1]==ban[xs][ys]&&visited[x][y]==false){
			visited[x][y]=true;
			if(dfs(x,y+1))return true;
		}
		if(x>=2&&ban[x-1][y]==ban[xs][ys]&&visited[x][y]==false){
			visited[x][y]=true;
			if(dfs(x-1,y))return true;
		}
		if(y>=2&&ban[x][y-1]==ban[xs][ys]&&visited[x][y]==false){
			visited[x][y]=true;
			if(dfs(x,y-1))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]=-1,visited[i][j]=false;
	
	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))cout<<"OK"<<endl;
	else cout<<"NG"<<endl;
	}
	return 0;
	}

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

struct board{
  int mass[102][102];
};
int gx,gy;
bool goal_flag;
void DFS(int x,int y,board b,int c){

    if(b.mass[y][x]!=c || b.mass[y][x]==0)return;
    if(x==gx&&y==gy){goal_flag=true;return;}
    b.mass[y][x]=0;
    DFS(x+1,y,b,c);
    DFS(x-1,y,b,c);
    DFS(x,y+1,b,c);
    DFS(x,y-1,b,c);
}

int main(){
  int h,w;
  int start_x,start_y;

  int n;
  int c,d,x,y;
  board b;
  while(1){
    cin>>w>>h;
    if(w==0&&h==0)break;
    cin>>start_x>>start_y;
    cin>>gx>>gy;
    cin>>n;
    for(int i=0;i<h+2;i++){
      for(int j=0;j<w+2;j++){
        b.mass[i][j]=0;
      }
    }

    for(int i=0;i<n;i++){
        cin>>c>>d>>x>>y;
        for(int j=0;j<2;j++){
          for(int k=0;k<4;k++){
            if(d==0){b.mass[y+j][x+k]=c;}
            else if(d==1){b.mass[y+k][x+j]=c;}
          }
        }
    }
    goal_flag=false;
    DFS(start_x,start_y,b,b.mass[start_y][start_x]);
    if(goal_flag)cout<<"OK";
    else cout<<"NG";
    cout<<endl;

  }
}

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

int C[102][102];
int ans;
int xg,yg;

void meiro(int W,int H,int c){
  if(W==xg && H==yg){
    ans = 1;
    return;
  }

  if(C[W][H]!=c){
    return;
  }

  C[W][H] = '.';

  meiro(W-1,H  ,c);
  meiro(W  ,H+1,c);
  meiro(W+1,H  ,c);
  meiro(W  ,H-1,c);
}

int main(){
  while(1){
    int w,h;
    cin >> w >> h;

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

    int xs,ys;
    cin >> xs >> ys;

    cin >> xg >> yg;

    int n;
    cin >> n;
    int c[n],d[n],x[n],y[n];

    int cbase;

    for(int i=0;i<n;i++){
      cin >> c[i] >> d[i] >> x[i] >> y[i];

      if(d[i]==0){
        for(int j=x[i];j<x[i]+4;j++){
          for(int k=y[i];k<y[i]+2;k++){
            C[j][k]=c[i];
          }
        }
      }
      if(d[i]==1){
        for(int j=x[i];j<x[i]+2;j++){
          for(int k=y[i];k<y[i]+4;k++){
            C[j][k]=c[i];
          }
        }
      }

      if(x[i]==1 &&y[i]==1){
        cbase = c[i];
      }
    }
    ans = 0;
    meiro(xs,ys,cbase);

    if(ans==1){
      cout << "OK" << endl;
    }else{
      cout << "NG" << endl;
    }
  }

  return 0;
}

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

int C[102][102];

void meiro(int W,int H,int c){
  if(C[W][H]!=c){
    return;
  }

  C[W][H] = -1;

  meiro(W-1,H  ,c);
  meiro(W  ,H+1,c);
  meiro(W+1,H  ,c);
  meiro(W  ,H-1,c);
}

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

    for(int i=0;i<102;i++){
      for(int j=0;j<102;j++){
        C[i][j] = 0;
      }
    }

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

    int n;
    cin >> n;

    int c,d,x,y;
    for(int i=0;i<n;i++){
      cin >> c >> d >> x >> y;

      if(d==0){
        for(int j=x;j<x+4;j++){
          for(int k=y;k<y+2;k++){
            C[j][k]=c;
          }
        }
      }else{
        for(int j=x;j<x+2;j++){
          for(int k=y;k<y+4;k++){
            C[j][k]=c;
          }
        }
      }
    }
    meiro(xs,ys,C[xs][ys]);

    if(C[xg][yg] == -1){
      cout << "OK" << endl;
    }
    if(C[xg][yg] != -1 || C[xs][ys] == 0){
      cout << "NG" << endl;
    }
  }

  return 0;
}

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

int xx[4] = {0, 1, 0, -1};
int yy[4] = {1, 0, -1, 0};
int block[101][101];
int already[101][101];
int w, h;
int xs, ys;
int xg, yg;
int n;
int dfs(int nowx, int nowy);

int main(){
  while(1){
    memset(block, 0, sizeof(block));
    memset(already, 0, sizeof(already));
    cin >> w >> h;
    if(w == 0 && h == 0) break;
    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;
      int high, wide;
      if(d){
	high = 4; wide = 2;
      }
      else{
	high = 2; wide = 4;
      }
      for(int j = 0; j < high; j++){
	for(int k = 0; k < wide; k++){
	  block[y+j][x+k] = c;
	}
      }
    }
    int ans = dfs(xs, ys);
    if(ans) cout << "OK" << endl;
    else cout << "NG" << endl;
  }
}

int dfs(int nowx, int nowy){
  already[nowy][nowx] = 1;
  if(nowx == xg && nowy == yg) return 1;
  for(int i = 0; i < 4; i++){
    int nextx = nowx + xx[i];
    int nexty = nowy + yy[i];
    if(0 < nextx && 0 < nexty && nextx <= w && nexty <= h && already[nexty][nextx] != 1 && block[nexty][nextx] == block[ys][xs]) return dfs(nextx, nexty);
  }
  return 0;
}