NYOJ 284 坦克大战 bfs + 优先队列

这类带权的边的图，直接广搜不行，要加上优先队列，这样得到的结果才是最优的，这样每次先找权值最小的，代码如下

 #include <stdio.h>
 #include <iostream>
 #include <queue>
 #include <string.h>
 using namespace std;
 typedef struct Node{
     int x, y;
     int step;
     friend bool operator < (const Node &a, const Node &b)
     {
         return a.step > b.step;
     }
 }Node;
 const int MAX =  + ;
 int N, M;
 int Map[MAX][MAX];
 int next[][] = {{, }, {, }, {, -}, {-, }};
 Node s, e;
 bool match(Node node)//判断是否到达终点
 {
     if (node.x == e.x && node.y == e.y)
         return true;
     return false;
 }
 bool check(Node node)//判断这个点是否能走
 {
     if (node.x <  || node.y <  || node.x >= N || node.y >= M || Map[node.x][node.y] == )
         return false;
     return true;
 }
 int bfs()
 {
     priority_queue<Node> q;//优先队列
     q.push(s);
     Node p1, p2;
     while (!q.empty())
     {
         p1 = q.top();
         q.pop();
         for (int i = ; i < ; i++)
         {
             p2.x = p1.x + next[i][];
             p2.y = p1.y + next[i][];
             p2.step = p1.step + Map[p2.x][p2.y];
             if (match(p2))
             {
                 return p2.step;
             }
             if (check(p2))
             {
                 Map[p2.x][p2.y] = ;
                 Node v = p2;
                 q.push(v);
             }
         }
     }
     return -;
 }
 int main()
 {
     char ch;
     while (~scanf("%d%d", &N, &M) && N + M)
     {
         for (int i = ; i < N; i++)
         {
             for (int j = ; j < M; j++)
             {
                 cin >> ch;
                 if (ch == 'Y')//起点
                 {
                     s.x = i;
                     s.y = j;
                     s.step = ;
                     Map[i][j] = ;
                 }
                 else if (ch == 'T')//终点
                 {
                     e.x = i;
                     e.y = j;
                     e.step = ;
                     Map[i][j] = ;
                 }
                 else if (ch == 'B')//普通砖块，权值为2
                 {
                     Map[i][j] = ;
                 }
                 else if (ch == 'E')//空地，权值为1
                 {
                     Map[i][j] = ;
                 }
                 else
                 {
                     Map[i][j] = ;//为0的时候表示此点不可走
                 }
             }
         }
         printf("%d\n", bfs());
     }

     return ;
 }