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 = 300 + 5;
int N, M;
int Map[MAX][MAX];
int next[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
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 < 0 || node.y < 0 || node.x >= N || node.y >= M || Map[node.x][node.y] == 0)
        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 = 0; i < 4; i++)
        {
            p2.x = p1.x + next[i][0];
            p2.y = p1.y + next[i][1];
            p2.step = p1.step + Map[p2.x][p2.y];
            if (match(p2))
            {
                return p2.step;
            }
            if (check(p2))
            {
                Map[p2.x][p2.y] = 0;
                Node v = p2;
                q.push(v);
            }
        }
    }
    return -1;
}
int main()
{
    char ch;
    while (~scanf("%d%d", &N, &M) && N + M)
    {
        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < M; j++)
            {
                cin >> ch;
                if (ch == 'Y')//起点
                {
                    s.x = i;
                    s.y = j;
                    s.step = 0;
                    Map[i][j] = 0;
                }
                else if (ch == 'T')//终点
                {
                    e.x = i;
                    e.y = j;
                    e.step = 0;
                    Map[i][j] = 1;
                }
                else if (ch == 'B')//普通砖块，权值为2
                {
                    Map[i][j] = 2;
                }
                else if (ch == 'E')//空地，权值为1
                {
                    Map[i][j] = 1;
                }
                else
                {
                    Map[i][j] = 0;//为0的时候表示此点不可走
                }
            }
        }
        printf("%d
", bfs());
    }

    return 0;
}