[BFS]A. 【例题1】走迷宫

A . 【 例 题 1 】 走 迷 宫 

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解析

简单的BFS模板题

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Code

#include <bits/stdc++.h>
#define N 1005
using namespace std;
const int dx[5] = {0, 1, -1, 0, 0};
const int dy[5] = {0, 0, 0, 1, -1};

int n, sx, sy, tx, ty;
int st[N * N][4], a[N][N], f[N][N];

int check (int x, int y)
{
    if (x <= n && y <= n && x >= 1 && y >= 1) return 1;
    return 0;
}

void bfs (int x, int y)
{
    int tail = 1, head = 0;
    st[1][1] = x; st[1][2] = y; st[1][3] = 0; f[x][y] = 1; 
    while (head < tail)
    {
        head ++;
        for (int i = 1; i <= 4; ++ i)
        {
            int ex = st[head][1] + dx[i];
            int ey = st[head][2] + dy[i];
            if (check (ex, ey)) 
            if (!a[ex][ey] && !f[ex][ey])
            {
                tail ++;
                f[ex][ey] = 1; 
                st[tail][1] = ex;
                st[tail][2] = ey;
                st[tail][3] = st[head][3] + 1; 
                if (ex == tx && ey == ty)
                {
                    printf ("%d", st[tail][3]);
                    return ;
                }
            }
        }
    }
}

int main ()
{
    scanf ("%d", &n);
    for (int i = 1; i <= n; ++ i)
     for (int j = 1; j <= n; ++ j)
      scanf ("%1d", &a[i][j]);
    scanf ("%d%d%d%d", &sx, &sy, &tx, &ty);
    bfs (sx, sy);
    return 0;
}