HDU1254 推箱子 BFS+优先队列

/* 箱子和人共同组成一个状态，用node来记录状态 使用优先队列，是因为只有箱子移动，记数才+1，并不是每次都+1， 从队列中选择记数最小的，进行下一步搜索 只使用优先队列不能保证结果是最小。 因为两个记数相同的状态，下一步的记数不一定相同 使用flag避免重复计算 */ #include <iostream> #include <queue> using namespace std; struct node { int ceil; int people_x,people_y; int box_x,box_y; bool operator<(const node& A)const { return ceil > A.ceil; } }; int map[9][9]; priority_queue<node> Q; int dir[4][2] = {{1, 0},{-1, 0},{0, 1},{0, -1}}; bool flag[9][9][9][9]; int main() { int t, m, n, i, j, px,py,bx,by, ans; node p, q; cin>>t; while(t--) { cin>>m>>n; memset(map, 0, sizeof(map)); memset(flag, 0, sizeof(flag)); ans = -1; for(i = 0; i < m; i++) { for(j = 0; j < n; j++) { cin>>map[i][j]; if(map[i][j] == 4) { p.people_x = i; p.people_y = j; } else if(map[i][j] == 2) { p.box_x = i; p.box_y = j; } } } while(!Q.empty())Q.pop(); p.ceil = 0;Q.push(p); flag[p.people_x][p.people_y][p.box_x][p.box_y] = 1; ans = -1; while(!Q.empty()) { p = Q.top();Q.pop(); px = p.people_x; py = p.people_y; bx = p.box_x; by = p.box_y; if(map[bx][by] == 3) { if(ans == -1 || ans > p.ceil) ans = p.ceil; } for(i = 0; i < 4; i++) { //越界 if((px+dir[i][0])<0 || (px+dir[i][0]) >= m || (py+dir[i][1]) < 0 || (py+dir[i][1]) >= n) continue; //墙 else if(map[px+dir[i][0]][py+dir[i][1]] == 1) continue; //不是箱子 else if(px+dir[i][0] != bx || py+dir[i][1] != by) { q = p; q.people_x += dir[i][0]; q.people_y += dir[i][1]; if(flag[q.people_x][q.people_y][q.box_x][q.box_y] == 0) { flag[q.people_x][q.people_y][q.box_x][q.box_y] = 1; Q.push(q); } } //是箱子 else if(px+dir[i][0] == bx && py+dir[i][1] == by) { //越界 if((px+2*dir[i][0])<0 || (px+2*dir[i][0]) >= m || (py+2*dir[i][1]) < 0 || (py+2*dir[i][1]) >= n) continue; //墙 else if(map[px+2*dir[i][0]][py+2*dir[i][1]] == 1) continue; //推箱子 q.box_x = px+2*dir[i][0]; q.box_y = py+2*dir[i][1]; q.people_x = px+dir[i][0];q.people_y = py+dir[i][1]; q.ceil = p.ceil + 1; if(flag[q.people_x][q.people_y][q.box_x][q.box_y] == 0) { flag[q.people_x][q.people_y][q.box_x][q.box_y] = 1; Q.push(q); } } } } cout<<ans<<endl; } return 0; }