POJ-1979 Red and Black（DFS）

题目链接：http://poj.org/problem?id=1979

深度优先搜索非递归写法

#include <cstdio>
#include <stack>

using namespace std;
const int MAX_W = 25, MAX_H = 25;
char Map[MAX_W][MAX_H+1];
int W, H;

int DFS(int sx, int sy);

int main()
{
    while (scanf("%d %d", &H, &W) == 2
           && W != 0 && H != 0) {
        for (int i = 0; i < W; i++)
            scanf("%s", Map[i]);
        for (int i = 0; i < W; i++)
            for (int j = 0; j < H; j++) {
                if (Map[i][j] == '@')
                    printf("%d
", DFS(i, j));
            }
    }
    return 0;
}

int DFS(int sx, int sy)
{
    int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
    int Visited[MAX_W][MAX_H] = {0};
    typedef pair<int, int> Position;
    stack<Position> sta;

    Visited[sx][sy] = 1;
    int num = 1;
    Map[sx][sy] = '.';
    sta.push(Position(sx, sy));

    while (!sta.empty()) {
        Position p = sta.top(); sta.pop();
        for (int i = 0; i < 4; i++) {
            int nx = p.first + dx[i], ny = p.second + dy[i];
            if (0 <= nx && nx < W && 0 <= ny && ny < H &&
                Map[nx][ny] == '.' && !Visited[nx][ny]) {
                sta.push(Position(nx, ny));
                Visited[nx][ny] = 1;
                num++;
            }
        }
    }
    return num;
}