[BFS] [洛谷] P1443 吗的便利

一看求最短路径

即为BFS

偷懒写DFS无限超时

#pragma GCC optimize(2)
#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <string>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <ctime>
#include <vector>
#include <fstream>
#include <list>
#include <iomanip>
#include <numeric>
using namespace std;
typedef long long ll;

const int MAXN = 1e6 + 10;

int arr[410][410];

struct node
{
    int x, y, step;

    node(int xa, int ya, int za)
    {
        x = xa;
        y = ya;
        step = za;
    }   
};

int movel[4][2] = { {1, -2}, {2, -1}, {2, 1}, {1, 2} };

ll n, m;

queue <node> Q;

void bfs(node a)
{
    Q.push(a);

    while(!Q.empty())
    {
        node b = Q.front();

        Q.pop();

        if( !(b.x < 1 || b.x > n || b.y < 1 || b.y > m || arr[b.x][b.y] >= 0 ) )
        {
            arr[b.x][b.y] = b.step;

            for(int i = 0; i < 4; i++)
            {
                
                Q.push(node(b.x + movel[i][0], b.y + movel[i][1], b.step + 1));


                Q.push(node(b.x - movel[i][0], b.y - movel[i][1], b.step + 1));
            }
        }
    }
}

void puts()
{
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= m; j++)
        {
            cout<<left<<setw(5)<<arr[i][j];
        }
        cout<<endl;
    }
}

int main()
{
    ios::sync_with_stdio(false);

    cin.tie(0);     cout.tie(0);

    cin>>n>>m;

    memset(arr, -1, sizeof(arr));

    //memset(used, 0, sizeof(arr));

    int x, y;

    cin>>x>>y;

    node in(x, y, 0);
    
    bfs(in);

    puts();


    return 0;
}