poj 2688 Cleaning Robot bfs+dfs

题目链接

首先bfs， 求出两两之间的距离， 然后dfs就可以。

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <cmath>
 #include <string>
 #include <queue>
 #include <vector>
 #include <map>
 #include <set>
 using namespace std;
 #define pb(x) push_back(x)
 #define ll long long
 #define mk(x, y) make_pair(x, y)
 #define mem(a) memset(a, 0, sizeof(a))
 #define lson l, m, rt<<1
 #define rson m+1, r, rt<<1|1
 #define mem1(a) memset(a, -1, sizeof(a))
 #define mem2(a) memset(a, 0x3f, sizeof(a))
 #define rep(i, a, n) for(int i = a; i<n; i++)
 #define ull unsigned long long
 typedef pair<int, int> pll;
 const double PI = acos(-1.0);
 const int inf = ;
 const double eps = 1e-;
 const int mod = 1e9+;
 const int dir[][] = { {-, }, {, }, {, -}, {, } };
 char c[][];
 int dis[][], vis[][], n, m, cnt, ans, used[];
 struct node
 {
     int x, y, step;
     node(){}
     node(int x, int y, int step):x(x), y(y), step(step){}
 };
 int bfs(pll s, pll e) {
     mem(vis);
     vis[s.first][s.second] = ;
     queue <node> q;
     q.push(node(s.first, s.second, ));
     while(!q.empty()) {
         node tmp = q.front(); q.pop();
         if(tmp.x == e.first && tmp.y == e.second)
             return tmp.step;
         for(int i = ; i<; i++) {
             int tmpx = tmp.x + dir[i][];
             int tmpy = tmp.y + dir[i][];
             if(tmpx>=&&tmpx<n&&tmpy>=&&tmpy<m&&!vis[tmpx][tmpy]&&c[tmpx][tmpy]!='x') {
                 q.push(node(tmpx, tmpy, tmp.step+));
                 vis[tmpx][tmpy] = ;
             }
         }
     }
     return ;
 }
 void dfs(int now, int num, int now_dis) {
     if(now_dis>=ans)
         return ;
     if(num == cnt-) {
         if(now_dis<ans) {
             ans = now_dis;
         }
         return ;
     }
     for(int i = ; i<cnt; i++) {
         if(!used[i]) {
             used[i] = ;
             dfs(i, num+, now_dis+dis[now][i]);
             used[i] = ;
         }
     }
 }
 pll point[];
 int main()
 {
     while(scanf("%d%d", &m, &n)) {
         if(n+m==)
             break;
         int sx, sy;
         mem(dis);
         cnt = ;
         for(int i = ; i<n; i++)
             scanf("%s", c[i]);
         for(int i = ; i<n; i++) {
             for(int j = ; j<m; j++) {
                 if(c[i][j] == 'o') {
                     c[i][j] = '';
                     point[].first = i;
                     point[].second = j;
                 }
                 if(c[i][j] == '*') {
                     point[cnt].first = i;
                     point[cnt++].second = j;
                 }
             }
         }
         for(int i = ; i<cnt; i++) {
             for(int j = i+; j<cnt; j++) {
                 dis[i][j] = dis[j][i] = bfs(point[i], point[j]);
             }
         }
         int flag = ;
         for(int i = ; i<cnt; i++) {
             if(dis[][i] == ) {
                 flag = ;
             }
         }
         if(flag) {
             puts("-1");
             continue;
         }
         mem(used);
         used[] = ;
         ans = inf;
         dfs(, , );
         printf("%d\n", ans);
     }
 }