Go: package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var (
	sc = bufio.NewScanner(os.Stdin)
)

type Color int

const (
	ColorBlack Color = iota
	ColorRed
)

var strByColor = map[Color]string{
	ColorBlack: "black",
	ColorRed:   "red",
}

func (c Color) String() string {
	return strByColor[c]
}

type Node struct {
	ID      int
	X, Y    int
	Color   Color
	NextIDs map[int]struct{}
}

func (n *Node) String() string {
	d, _ := json.Marshal(n)
	return string(d)
}

type Map struct {
	Width, Height int
	Nodes         map[int]*Node
}

func (m *Map) GetByID(id int) *Node {
	return m.Nodes[id]
}

func (m *Map) Get(x, y int) *Node {
	return m.Nodes[m.getID(x, y)]
}

func (m *Map) SetColor(x, y int, c Color) {
	m.Nodes[m.getID(x, y)].Color = c
}

func (m *Map) getID(x, y int) int {
	return x + y*m.Width
}

func (m *Map) init() {
	for x := 1; x <= m.Width; x++ {
		for y := 1; y <= m.Height; y++ {
			id := m.getID(x, y)
			m.Nodes[id] = &Node{ID: id, X: x, Y: y}
		}
	}
	for x := 1; x <= m.Width; x++ {
		for y := 1; y <= m.Height; y++ {
			nextIDs := map[int]struct{}{}
			if x > 1 {
				nextIDs[m.getID(x-1, y)] = struct{}{}
			}
			if x < m.Width {
				nextIDs[m.getID(x+1, y)] = struct{}{}
			}
			if y > 1 {
				nextIDs[m.getID(x, y-1)] = struct{}{}
			}
			if y < m.Height {
				nextIDs[m.getID(x, y+1)] = struct{}{}
			}
			m.Get(x, y).NextIDs = nextIDs
		}
	}
}

func NewMap(w, h int) *Map {
	m := &Map{Width: w, Height: h, Nodes: map[int]*Node{}}
	m.init()
	return m
}

type Searcher struct {
	Map        *Map
	queue      []*Node
	touchedIDs map[int]struct{}
	visitedIDs map[int]struct{}
}

func NewSearcher(m *Map) *Searcher {
	return &Searcher{
		Map:        m,
		queue:      []*Node{},
		touchedIDs: map[int]struct{}{},
		visitedIDs: map[int]struct{}{},
	}
}

func (s *Searcher) Search(start *Node) {
	s.enqueue(start)

	for {
		if len(s.queue) == 0 {
			break
		}
		for nextID := range s.dequeue().NextIDs {
			n := s.Map.GetByID(nextID)
			if n.Color == ColorRed || s.hasTouched(n) {
				continue
			}
			s.enqueue(n)
		}
	}
}

func (s *Searcher) VisitedNodeCount() int {
	return len(s.visitedIDs)
}

func (s *Searcher) hasTouched(n *Node) bool {
	_, ok := s.touchedIDs[n.ID]
	return ok
}

func (s *Searcher) enqueue(n *Node) {
	s.queue = append(s.queue, n)
	s.touchedIDs[n.ID] = struct{}{}
}

func (s *Searcher) dequeue() *Node {
	n := s.queue[0]
	s.queue = s.queue[1:]
	s.visitedIDs[n.ID] = struct{}{}
	return n
}

func main() {
	for sc.Scan() {
		if sc.Text() == "0 0" {
			break
		}
		chunks := strings.Split(sc.Text(), " ")
		w, _ := strconv.Atoi(chunks[0])
		h, _ := strconv.Atoi(chunks[1])

		m := NewMap(w, h)

		// Set colors
		var start *Node
		for y := 1; y <= h; y++ {
			sc.Scan()
			for i, c := range sc.Text() {
				switch c {
				case '.', '@':
					m.SetColor(i+1, y, ColorBlack)
					if c == '@' {
						start = m.Get(i+1, y)
					}
				case '#':
					m.SetColor(i+1, y, ColorRed)
				}
			}
		}

		// Search
		s := NewSearcher(m)
		s.Search(start)
		fmt.Println(s.VisitedNodeCount())
	}
}

Python: #演習2-22
def solve(w,h,tile):
    # スタート地点探索
    ok = False
    for y in range(h):
        for x in range(w):
            if tile[y][x] == "@":
                s_x = x
                s_y = y
                ok = True
                break
        if ok:
            break
    # 幅優先探索
    count = 0
    check = [[s_x, s_y]]
    check_map = [[False for j in range(w)] for i in range(h)]
    while len(check) > 0:
        x, y = check.pop(0)
        if x in range(w) and y in range(h):
            if check_map[y][x] == False:
                if tile[y][x] == "." or tile[y][x] == "@":
                    check_map[y][x] = True
                    count += 1
                    check.append([x, y-1])
                    check.append([x, y+1])
                    check.append([x+1, y])
                    check.append([x-1, y])
    return count

while True:
    try:
        w, h = map(int, input().split())
        if w == 0:
            break
        tile = [""] * h
        for i in range(h):
            tile[i] = input()

        print(solve(w,h,tile))
    except:
        break

Python: mx = [0, 1, 0, -1]
my = [-1, 0, 1, 0]

while True:
    w, h = map(int, input().split())
    if w == h == 0:
        break
    tiles = [[i for i in input()] for j in range(h)]
    ax = ay = 0
    for i in range(h):
        for j in range(w):
            if tiles[i][j] == '@':
                ax, ay = j, i
    que = [(ax, ay)]
    tiles[ay][ax] = '#'
    cnt = 1

    while 0 < len(que):
        new_que = []
        for x, y in que:
            for i in range(4):
                nx, ny = x + mx[i], y + my[i]
                print(nx, ny)
                if 0 <= nx <= w - 1 and 0 <= ny <= h - 1:
                    if tiles[ny][nx] == '.':
                        cnt += 1
                        new_que.append((nx, ny))
                        tiles[ny][nx] = '#'
        que = new_que
    print(cnt)

Python: while 1:
	x,y = list(map(int,input().split()))
	if x == 0:
		break

	pp = [1,-1,0,0]
	qq = [0,0,1,-1]
	m = []
	for i in range(y):
		m.append(list(input()))
		if '@' in m[-1]:
			ss = m[-1].index('@')
			tt = i
	cnt = 0

	def move (cx,cy):
		global cnt
		if cy >= y or cy < 0 or cx >= x or cx < 0:
			return
		if m[cy][cx] == '.' or  m[cy][cx] == '@':
			cnt += 1
			m[cy][cx] = '0'
			for i in range(4):
				move(cx + pp[i],cy + qq[i])
	move(ss,tt)
	print(cnt)

Python: while True:
    W,H = [int(x) for x in input().split()]
    if W==0 and H==0:
        exit()
    tiles = []
    X = 0
    Y = 0
    for i in range(H):
        tiles.append(input())
        if '@' in tiles[i]:
            Y = i
            X = tiles[i].index('@')
    d = [[9999 for j in range(H*W)] for i in range(H*W)]
    for i in range(H*W):
        d[i][i] = 0
    for i in range(H):
        for j in range(W):
            if j>0:
                if tiles[i][j] in '.@' and tiles[i][j-1] in '.@':
                    d[W*i+j][W*i+j-1] = 1
            if j<W-1:
                if tiles[i][j] in '.@' and tiles[i][j+1] in '.@':
                    d[W*i+j][W*i+j+1] = 1
            if i>0:
                if tiles[i][j] in '.@' and tiles[i-1][j] in '.@':
                    d[W*i+j][W*i+j-W] = 1
            if j<H-1:
                if tiles[i][j] in '.@' and tiles[i+1][j] in '.@':
                    d[W*i+j][W*i+j+W] = 1
    for k in range(H*W):
        for i in range(H*W):
            for j in range(H*W):
                if d[i][j] > d[i][k]+d[k][j]:
                    d[i][j] = d[i][k]+d[k][j]
    cnt = 0
    for i in range(H*W):
        if d[X+Y*H][i]<9999:
            cnt += 1
    print(cnt)

Python: def location(field, wanted):
    for i, row in enumerate(field):
        for j, cell in enumerate(row):
            if cell == wanted:
                return i, j
def count(field, wanted):
    result = 0
    for row in field:
        for cell in row:
            if cell == wanted:
                result += 1
    return result
def neighborhood(center, w, h):
    i, j = center
    return filter(lambda x: 0 <= x[0] and x[0] < h and 0 <= x[1] and x[1] < w,
                  [                (i - 1, j    ),
                   (i    , j - 1),                 (i    , j + 1),
                                   (i + 1, j    )])
printed_later = []
while True:
    #入力
    w, h = map(int, input().split())
    if(w == 0 and h == 0):
        break
    field = []  # strの配列すなわちcharの配列の配列 '.':黒 '#':赤 '@':スタート (',':到達可能)
    for i in range(h):
        field.append(list(input()))
    #出力　幅優先探索
    queue = [location(field,'@')]
    field[queue[0][0]][queue[0][1]] = ','
    while len(queue) > 0:
        for cell in neighborhood(queue.pop(0), w, h):
            if field[cell[0]][cell[1]] == '.':
                queue.append(cell)
                field[cell[0]][cell[1]] = ','
    printed_later.append(count(field, ','))
for line in printed_later:
    print(line)