rt。$387$ 的 $D$ 题求调。

#include <bits/stdc++.h>
using namespace std;
const int dx[] = {0, 0, 1, -1};
const int dy[] = {1, -1, 0, 0};
struct Point {
    int x, y, dist,derect;
};

bool isValid(int x, int y, int n, int m, const vector<vector<char>>& maze) {
    return x >= 1 && x <= n && y >= 1 && y <= m && (maze[x][y] == '.'||maze[x][y]=='G');
}

int bfsMaze(const vector<vector<char>>& maze, const Point& start, const Point& end) {
    int n = maze.size();
    int m = maze[0].size();
    vector<vector<bool>> visited(n, vector<bool>(m, false));
    queue<Point> q;
    q.push(start);
    visited[start.x][start.y] = true;
    while (!q.empty()) {
        Point current = q.front();
        q.pop();
        if (current.x == end.x && current.y == end.y) {
            return current.dist;
        }
        for (int i = 0; i < 4; ++i) {
            int newX = current.x + dx[i];
            int newY = current.y + dy[i];
            Point s={newX, newY, current.dist + 1,i};
            if (isValid(newX, newY, n, m, maze) && !visited[newX][newY] && current.derect!=s.derect) {
                visited[newX][newY] = true;
                q.push({newX, newY, current.dist + 1,i});
            }
        }
    }
    return -1;
}
vector<vector<char>>maze(1005,vector<char>(1005));
int main() {
	int H,W;
	cin>>H>>W;
	Point start = {0,0,0,-1};
	Point end = {H,W,0,-1}; 
	for(int i=1;i<=H;i++){
		for(int j=1;j<=W;j++){
			cin>>maze[i][j];
			if(maze[i][j]=='S')start={i,j,0,-1};
			else if(maze[i][j]=='G')end={i,j,0,-1};
		}
	}
    int result = bfsMaze(maze, start, end);
    if (result != -1) {
        cout << result << endl;
    } else {
        cout << "-1" << endl;
    }
    return 0;
}

代码由 $\text{AI}$ 生成的 $\text{BFS}$ 模板改的。