hdoj1240 Asteroids!

题意:

  BFS的小小变形,场景由二维迷宫变成三维空间的迷宫,基本框架是不变的.
  这个题目就是考耐心嘛,毕竟就像一篇阅读理解,只需要看懂那个slice就是指z轴上不同点的平面就可以了.另外,需要注意题目中给出的起点的顺序是:start_y(列), start_x(行), start_z,这个需要跟自己的数组中的每一维的意义对应起来,否则结果就会不对.然后还要注意,每走到一个点,都会有6个方向的点(上\下\左\右\前\后)待探索.

代码:

// 0ms, 1804K// BFS on a cubic maze#include <iostream>#include <cstring>#include <queue>using namespace std;struct Location {    int x, y, z, step;    Location(int x, int y, int z, int s) : x(x), y(y), z(z), step(s) {    }};const int FAIL_VALUE = -1;const int DIR[6][3] = { {1,0,0}, {-1,0,0}, {0,1,0}, {0,-1,0}, {0,0,1}, {0,0,-1} };  // 6 directions every explorationconst int MAX_DIMEN(11);char maze[MAX_DIMEN][MAX_DIMEN][MAX_DIMEN];bool isVisited[MAX_DIMEN][MAX_DIMEN][MAX_DIMEN];int dimen;int _x2, _y2, _z2;  // coordinates of target pointint _x1, __y1, _z1; // coordinates of start pointbool isValid(const int& x, const int& y, const int& z) {    return x >= 0 && y >= 0 && z >= 0 &&            x < dimen && y < dimen && z < dimen;}int bfs() {    memset(isVisited, false, sizeof isVisited); // initial visit-array    queue<Location> locations;    isVisited[_x1][__y1][_z1] = true;    locations.push( Location(_x1, __y1, _z1, 0) );    while (!locations.empty()) {         Location cur = locations.front();        //cout << _debug << "\t" << cur.step << endl;        locations.pop();        if (cur.x == _x2 && cur.y == _y2 && cur.z == _z2) { // if arriving at the target point            return cur.step;        }        for (int dir = 0; dir < 6; ++dir) {            int xx = cur.x + DIR[dir][0];            int yy = cur.y + DIR[dir][1];            int zz = cur.z + DIR[dir][2];            if (isValid(xx, yy, zz) && !isVisited[zz][xx][yy] && maze[zz][xx][yy] == 'O') { // those which can reach                isVisited[zz][xx][yy] = true;                locations.push( Location(xx, yy, zz, cur.step + 1) );            }        }    }    return FAIL_VALUE;}int main() {//  freopen("in.txt", "r", stdin);    char op[10];    while (cin >> op >> dimen) {    // 'START N'        /* input phase */        int x, y, z;        for (int z = 0; z < dimen; ++z) {            for (int x = 0; x < dimen; ++x) {                for (int y = 0; y < dimen; ++y) {                    cin >> maze[z][x][y];                }            }        }        cin >> __y1 >> _x1 >> _z1;  // mind the order of input...        cin >> _y2 >> _x2 >> _z2;         cin >> op;  // 'END'        /* process phase */        int need_step = bfs();        if (need_step == FAIL_VALUE) {            cout << "NO ROUTE" << endl;        } else {            cout << dimen << " " << need_step << endl;        }    }    return 0;}