Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var (
	direction1 = [][]int{ // 奇数段目の移動方向
		{-1, 0}, {1, 0}, {0, -1}, {0, 1}, {1, -1}, {1, 1},
	}
	direction2 = [][]int{ // 偶数段目の移動方向
		{-1, -1}, {0, -1}, {1, 0}, {0, 1}, {-1, 1}, {-1, 0},
	}
)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		m, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		if m == 0 && n == 0 {
			break
		}
		// initialize district_map
		/*
			district_map = [
				[-1, -1,  -1,  -1,  -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, -1,  -1,  -1,  -1]
			]
		*/
		district_map := make([][]int, n+2)
		for i := range district_map {
			district_map[i] = make([]int, m+2)
		}
		tmp1 := make([]int, m+2)
		for i := range tmp1 {
			tmp1[i] = -1
		}
		district_map[0] = tmp1
		district_map[n+1] = tmp1
		for i := 1; i < n+1; i++ {
			district_map[i] = make([]int, m+2)
			district_map[i][0] = -1
			district_map[i][m+1] = -1
			for j := 1; j < m+1; j++ {
				district_map[i][j] = INF
			}
		}

		scanner.Scan()
		s, _ := strconv.Atoi(scanner.Text())
		for i := 0; i < s; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			x, _ := strconv.Atoi(buf_[0])
			y, _ := strconv.Atoi(buf_[1])
			Search(Point{x, y}, district_map, m, n)
		}
		ans := 0
		scanner.Scan()
		t, _ := strconv.Atoi(scanner.Text())
		for i := 0; i < t; i++ {
			scanner.Scan()
			buf__ := strings.Split(scanner.Text(), " ")
			x, _ := strconv.Atoi(buf__[0])
			y, _ := strconv.Atoi(buf__[1])
			z := Count(Point{x, y}, district_map, m, n)
			ans = max(ans, z)
		}
		fmt.Println(ans)
	}
}

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

type Point struct {
	x, y int
}

type Entry struct {
	hop   int
	point Point
}

func Search(p Point, mp [][]int, m, n int) {
	que := make([]Entry, 0)
	que = append(que, Entry{0, p})
	check := make([][]bool, n+2)
	for i := range check {
		check[i] = make([]bool, m+2)
	}
	check[p.y][p.x] = true
	mp[p.y][p.x] = 0
	var direction [][]int
	for len(que) > 0 {
		tmp := que[0]
		que = que[1:]
		dist, point := tmp.hop, tmp.point
		if point.y%2 == 0 {
			direction = direction1
		} else {
			direction = direction2
		}
		for _, d := range direction {
			nx, ny := point.x+d[0], point.y+d[1]
			if !check[ny][nx] && mp[ny][nx] != -1 {
				check[ny][nx] = true
				if mp[ny][nx] > dist+1 {
					mp[ny][nx] = dist + 1
				}
				que = append(que, Entry{dist + 1, Point{nx, ny}})
			}
		}
	}
}

func Count(p Point, mp [][]int, m, n int) int {
	que := make([]Entry, 0)
	que = append(que, Entry{0, p})
	check := make([][]bool, n+2)
	for i := range check {
		check[i] = make([]bool, m+2)
	}
	check[p.y][p.x] = true
	ans := 1
	var direction [][]int
	for len(que) > 0 {
		tmp := que[0]
		que = que[1:]
		dist, point := tmp.hop, tmp.point
		if point.y%2 == 0 {
			direction = direction1
		} else {
			direction = direction2
		}
		for _, d := range direction {
			nx, ny := point.x+d[0], point.y+d[1]
			if !check[ny][nx] && mp[ny][nx] != -1 {
				check[ny][nx] = true
				if mp[ny][nx] > dist+1 {
					ans++
				}
				que = append(que, Entry{dist + 1, Point{nx, ny}})
			}
		}
	}
	return ans
}

C++: #include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<cassert>
#include<vector>
#include<deque>
using namespace std;
typedef pair<int,int> P;
int n,m,s,cnt;
int Cost[10][100][100];
int mincost[100][100];
bool visited[100][100];
int dx[2][6] = {{-1,+0,1,0,-1,-1},{+0,+1,1,1,0,-1}};
int dy[2][6] = {{-1,-1,0,1,+1,+0},{-1,-1,0,1,1,+0}};

void dfs(int p,int x,int y,int cost)
{
  for(int i=0;i<6;i++)
    {
      int nx = x + dx[y%2][i];
      int ny = y + dy[y%2][i];
      if(!(0 <= nx && nx < m && 0 <= ny && ny < n))
	continue;

      if(Cost[p][ny][nx] > cost)
	{
	  Cost[p][ny][nx] = cost;
	  dfs(p,nx,ny,cost+1);
	}
    }
}

void dfs2(int x,int y,int cost)
{
  for(int i=0;i<6;i++)
    {
      int nx = x + dx[y%2][i];
      int ny = y + dy[y%2][i];
   
      if(!(0 <= nx && nx < m && 0 <= ny && ny < n))
	continue;

      if(mincost[ny][nx] <= cost)
	continue;    

      
      mincost[ny][nx] = cost;


      bool ok = true;
      for(int j=0;j<s;j++)
	if(Cost[j][ny][nx] <= cost)
	  {
	    ok = false;
	    break;
	  }

      if(ok)
	{
	  if(!visited[ny][nx])
	    cnt++;
	  visited[ny][nx] = true;
	  dfs2(nx,ny,cost+1);
	}

      

    }

}

int main()
{
  while(true)
    {
      cin >> n;
      if(!n)
	break;
      cin >> m;

    
     
      scanf("%d",&s);


      for(int i=0;i<s;i++)
	for(int j=0;j<n;j++)
	  for(int k=0;k<m;k++)
	    Cost[i][j][k] = (1<<29);
      
      for(int i=0;i<s;i++)
	{
	  int x,y;
	  scanf("%d %d",&x,&y);
	  x--,y--;
	  Cost[i][y][x] = 0;
	  dfs(i,x,y,1);
	}

      int t;
      scanf("%d",&t);

      int mex = 0;
      for(int i=0;i<t;i++)
	{
	  int p,q;
	  scanf("%d %d",&p,&q);
	  cnt = 1;
	  p--,q--;
	  
	  for(int j=0;j<n;j++)
	    for(int k=0;k<m;k++)
	      mincost[j][k] = (1<<29),visited[j][k] = false;
	  mincost[q][p] = 0;
	  visited[q][p] = true;
	  dfs2(p,q,1);
	  
	  mex = max(mex,cnt);
	}
      cout << mex << endl;

    }
  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
int INF=(1<<24);
int dy[6]={0,-1,-1,0,1,1};
int dx[2][6]={
  {-1,-1,0,1,0,-1},{-1,0,1,1,1,0}
};
int W,H,n,m,I;
int ty[100],tx[100];
int uy[100],ux[100];
int v[100][100];

queue <int> Qy;
queue <int> Qx;
queue <int> Qcnt;
queue <int> Qid;

bool input();
void init(int);
void solve();
int bfs();

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

int bfs(){
  int y,x,ny,nx,cnt,id,res=0;
  while(!Qy.empty()){
    y=Qy.front();Qy.pop();
    x=Qx.front();Qx.pop();
    cnt=Qcnt.front();Qcnt.pop();
    id=Qid.front();Qid.pop();


    if(id==n+I)res++;

    for(int i=0;i<6;i++){
      ny=y+dy[i];
      nx=x+dx[y%2][i];
      if(ny<0||nx<0||ny>=H||nx>=W)continue;
      if(cnt+1>=v[ny][nx])continue; 
      v[ny][nx]=cnt+1;
      Qy.push(ny);
      Qx.push(nx);
      Qcnt.push(cnt+1);
      Qid.push(id);
    
    }
  }
  return res;
}

void solve(){
  int ans=0;
  for(I=0;I<m;I++){
    init(I);
    ans=max(ans,bfs());
  }
  cout<<ans<<endl;
}

bool input(){
  cin>>W>>H;
  if(W==0&&H==0)return false;
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>tx[i]>>ty[i];
    ty[i]--;
    tx[i]--;
  }
  cin>>m;
  for(int i=0;i<m;i++){
    cin>>ux[i]>>uy[i];
    uy[i]--;
    ux[i]--;
  }
  return true;
}

void init(int s){
  for(int i=0;i<100;i++){
    for(int j=0;j<100;j++){
      v[i][j]=INF;
    }
  }
  while(!Qy.empty()){
    Qy.pop();
    Qx.pop();
    Qcnt.pop();
    Qid.pop();
  }
  

  for(int i=0;i<n;i++){
    Qy.push(ty[i]);
    Qx.push(tx[i]);
    Qcnt.push(0);
    Qid.push(i);
    v[ty[i]][tx[i]]=0;
  }
  Qy.push(uy[s]);
  Qx.push(ux[s]);
  Qcnt.push(0);
  Qid.push(n+s);
  v[uy[s]][ux[s]]=0;
}