Fire Game FZU

来源：互联网发布：pdu协议数据单元编辑：程序博客网时间：2024/06/02 04:54

这个题题意是两个人在草地上选两点为起点放火，问能不能把草地烧完，能的话画出最短的时间。做法就是选两个起点进行BFS，由于图比较小，可以直接枚举任意两个点进行BFS，选取最短时间

这是一个有两个起点的BFS，起初我是打算开两个队列，然后同时进行BFS，然后错了，，后来一想，即便是把所有的点都放在同一个队列里，也是相当于从两个点开始的BFS，然而还是Wrong，后来想是不是判断不能燃烧所有的草地那个地方错了，本来我是通过一个grass_num记录一共有多少块草地，然后每往队列里压入一个就自减，return的时候判断grass_num是不是为0，后来改成了遍历了。。遍历就过了

//leehaoze#include <iostream>#include <deque>#include <string>#include <vector>#include <queue>#include <cstdio>#include <stack>#include <algorithm>#include <cstring>#include <cctype>#include <cstdio>#include <cmath>#include <cstdlib>using namespace std;const int INF = 1 << 29;#define INC_SAT(val) (val = ((val)+1 > (val)) ? (val)+1 : (val))#define ARR_SIZE(a) ( sizeof( (a) ) / sizeof( (a[0]) ) )#define ULL unsigned long long#define MAXN (10 + 5)struct Pos {    Pos(int x, int y, int step) : x_(x), y_(y), step_(step) {}    int x_, y_, step_;};int Move_X[] = {0, 0, 1, -1};int Move_Y[] = {1, -1, 0, 0};int T;int N, M, grass_num;char map[MAXN][MAXN];bool visit[MAXN][MAXN];vector<Pos> V;void Input() {    scanf("%d%d", &N, &M);    getchar();    grass_num = 0;    V.clear();    for (int i = 0; i < N; ++i) {        for (int j = 0; j < M; ++j) {            scanf("%c", &map[i][j]);            if (map[i][j] == '#') {                grass_num++;                V.push_back(Pos(i, j, 0));            }            visit[i][j] = false;        }        getchar();    }}bool Legal(int dx, int dy) {    return dx >= 0 && dx < N && dy >= 0 && dy < M && !visit[dx][dy] && map[dx][dy] == '#';}int BFS(Pos startA, Pos startB) {    queue<Pos> Q;    Q.push(startA);    Q.push(startB);    visit[startA.x_][startA.y_] = true;    visit[startB.x_][startB.y_] = true;    while (!Q.empty()) {        Pos now = Q.front();        Q.pop();        for (int i = 0; i < 4; ++i) {            int dx = now.x_ + Move_X[i];            int dy = now.y_ + Move_Y[i];            if (Legal(dx, dy)) {                visit[dx][dy] = true;                Q.push(Pos(dx, dy, now.step_ + 1));            }        }        if (Q.empty()) {            return now.step_;        }    }}bool Judge() {    for (int i = 0; i < N; ++i) {        for (int j = 0; j < M; ++j) {            if (map[i][j] == '#' && !visit[i][j]) {                return false;            }        }    }    return true;}void Clear_Visit() {    for (int i = 0; i < N; ++i) {        for (int j = 0; j < M; ++j) {            visit[i][j] = false;        }    }}void Enumerate() {    int ans = MAXN * MAXN;    int size = (int) V.size();    for (int i = 0; i < size; ++i) {        for (int j = i; j < size; ++j) {            Clear_Visit();            int temp = BFS(V[i], V[j]);            if (Judge()) {                ans = min(ans, temp);            }        }    }    if (ans == MAXN * MAXN)        cout << -1 << endl;    else        cout << ans << endl;}int main() {#ifdef LOCAL    freopen("IN.txt", "r", stdin);#endif    std::ios::sync_with_stdio(false);    scanf("%d", &T);    getchar();    for (int i = 0; i < T; ++i) {        Input();        cout << "Case " << i + 1 << ": ";        Enumerate();    }}

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