洛谷 P1649 [USACO07OCT]障碍路线Obstacle Course

题目传送门

解题思路:

bfs走迷宫.

AC代码:

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue> 

using namespace std;

int n,x,y,bx,by,ans = 199999999;
int wayx[4] = {-1,0,1,0};
int wayy[4] = {0,-1,0,1};
char a[101][101];
bool vis[101][101][4];
struct kkk {
    int step,xx,yy;
    int direction;
}e;
queue<kkk> q;

inline void bfs() {
    for(int i = 0;i <= 3; i++) {
        kkk k;
        k.step = 0;
        k.direction = i;
        k.xx = x;
        k.yy = y;
        q.push(k);
        vis[x][y][i] = 1;
    }
    while(!q.empty()) {
        kkk p = q.front();
        q.pop();
        if(p.xx == bx && p.yy == by) ans = min(ans,p.step);
        for(int i = 0;i <= 3; i++) {
            kkk o;
            if((i + p.direction) % 2 == 1) {
                o.direction = i;
                o.step = p.step + 1;
                o.xx = p.xx;
                o.yy = p.yy;
            }
            if(i == p.direction) {
                o.direction = i;
                o.step = p.step;
                o.xx = p.xx + wayx[i];
                o.yy = p.yy + wayy[i];    
            }
            if(!vis[o.xx][o.yy][o.direction] && a[o.xx][o.yy] != 'x' && o.xx >= 1 && o.xx <= n && o.yy >= 1 && o.yy <= n) {
                q.push(o);
                vis[o.xx][o.yy][o.direction] = 1;
            }
        }
    }
}

int main() {
    scanf("%d",&n);
    for(int i = 1;i <= n; i++)
        for(int j = 1;j <= n; j++) {
            cin >> a[i][j];
            if(a[i][j] == 'A') x = i,y = j;
            if(a[i][j] == 'B') bx = i,by = j; 
        }
    bfs();
    if(ans == 199999999) printf("-1");
    else
        printf("%d",ans);
    return 0;
}