HDU 1242 Rescue （BFS+优先队列）

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从天使的位置开始，直到找到r，优先队列每次选择最短时间的路

#include<iostream>#include<algorithm>#include<cstring>#include<string>#include<sstream>#include<queue>using namespace std;typedef long long LL;const int INF = 0x3f3f3f3f;const int M = 1010;struct node{int x, y, step;bool operator <(const node &b)const{return step > b.step;}};int n, m;priority_queue<node>q;char mp[210][210];int sx, sy;bool vis[210][210];int dir[][2] = { 1,0,-1,0,0,1,0,-1 };int bfs(){node st;st.x = sx;st.y = sy;st.step = 0;vis[sx][sy] = 1;q.push(st);while (!q.empty()){node nw = q.top();q.pop();if (mp[nw.x][nw.y] == 'r'){return nw.step;}for (int i = 0; i < 4; ++i){int xx = nw.x + dir[i][0];int yy = nw.y + dir[i][1];if(xx<0 ||xx>=n ||yy<0||yy>=m ||vis[xx][yy])continue;if(mp[xx][yy]=='#')continue;if (mp[xx][yy] == 'x'){vis[xx][yy] = 1;node nx;nx.x = xx;nx.y = yy;nx.step = nw.step + 2;q.push(nx);}else{vis[xx][yy] = 1;node nx;nx.x = xx;nx.y = yy;nx.step = nw.step + 1;q.push(nx);}}}return -1;}int main(){while (~scanf("%d%d", &n, &m)){for (int i = 0; i < n; ++i){for (int j = 0; j < m; ++j){cin >> mp[i][j];if (mp[i][j] == 'a'){sx = i;sy = j;}}}memset(vis, 0, sizeof(vis));int flag=bfs();if (flag == -1){puts("Poor ANGEL has to stay in the prison all his life.");}else{printf("%d\n", flag);}}return 0;}

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