ACM篇：FZU 2150 -- Fire Game

bfs
枚舉兩個起點（可能相同）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <vector>
#include <cstring>
#include <algorithm>

using namespace std;

struct Point
{
    int r, c;
    Point(int r=0,int c=0): r(r), c(c) {}
};
const int MAX = 10;
const int SUP = 1999999999;

int n;
int m;
int tot;
bool board[MAX+2][MAX+2];
int firetime[MAX+2][MAX+2];
vector<Point> grass;

int readchar()
{
    int ch;
    while (ch = getchar())
    {
        if (ch == '.' || ch == '#')
            return ch;
    }
}
int read_board()
{
    memset(board, 0, sizeof(board));
    grass.clear();
    scanf("%d%d\n", &n, &m);
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
        {
            if (readchar() == '#')
            {
                board[i][j] = true;
                grass.push_back(Point(i, j));
            }
        }
    return grass.size();
}
bool inside(Point u)
{
    return (u.r >= 1 && u.r <= n && u.c >= 1 && u.c <= m);
}

int _bfs(int r, int c, int rr, int cc)
{
    static const int ROW[] = {-1, 0, 1, 0};
    static const int COL[] = {0, 1, 0, -1};
    queue<Point> q;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            firetime[i][j] = SUP;

    q.push(Point(r, c));
    if (rr != r || cc != c) 
        q.push(Point(rr,cc));
    firetime[r][c] = firetime[rr][cc] = 0;
    int cnt = 0;
    int cost = 0;
    while (!q.empty())
    {
        Point u = q.front();
        q.pop();
        cnt++;

        for (int i = 0; i < 4; i++)
        {
            Point v = Point(u.r + ROW[i], u.c + COL[i]);
            if (inside(v) && board[v.r][v.c] && firetime[v.r][v.c] > firetime[u.r][u.c] + 1)
            {
                cost = max(cost, firetime[v.r][v.c] = firetime[u.r][u.c] + 1);
                q.push(v);
            }
        }
    }
    return (cnt == tot) ? cost : -1;
}
int _enumberate()
{
    int ret = -1;
    int tmp;
    for (int i = 0; i < tot; i++)
    {
        for (int j = i; j < tot; j++)
        {
            if ((tmp = _bfs(grass[i].r, grass[i].c, grass[j].r, grass[j].c)) != -1)
            {
                if (ret == -1)
                    ret = tmp;
                else 
                    ret = min(ret, tmp);
            }
        }
    }
    return ret;
}

int main()
{
    int T;
    int kase = 0;
    int ans = -1;
    scanf("%d", &T);
    while (++kase <= T)
    {
        tot = read_board(); 
        ans = _enumberate();
        printf("Case %d: %d\n", kase, ans);
    }
    return 0;
}