203. 迷宫的最短路径（挑战程序设计竞赛）

地址 https://www.papamelon.com/problem/203

解答
BFS的搜索方案是一步步扩展，天生具有搜索最短路径性质。
我们可以使用宽度优先搜索 BFS进行搜索

#include <iostream>
#include <vector>
#include <queue>

using namespace std;

const int N = 110;
char arr[N][N];
int  vis[N][N];
int n, m;

int addx[4] = { 0,0,1,-1 };
int addy[4] = { 1,-1,0,0 };

int bfs(int sx, int sy) {
	queue <vector<int>> q;
	q.push({ sx,sy,0 });
	vis[sx][sy] = 1;
	while (!q.empty()) {
		int currX = q.front()[0];
		int currY = q.front()[1];
		int step = q.front()[2];
		q.pop();
		//cout << currX << " " << currY  << " " << step<< endl;
		for (int i = 0; i < 4; i++) {
			int x = currX + addx[i];
			int y = currY + addy[i];

			if (x >= 0 && x < n&&y >= 0 && y < m && vis[x][y] == 0 && arr[x][y] != '#') {
				if (arr[x][y] == 'G') { 
					return step+1;
				}
				q.push({x,y,step+1});
				vis[x][y] = 1;
			}
		}
	}

	return -1;
}

int main() {
	cin >> n >> m;
	pair<int, int> start;
	pair<int, int> end;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			cin >> arr[i][j];
			if (arr[i][j] == 'S') { start.first = i; start.second = j; }
		}
	}

	cout << bfs(start.first, start.second);
	

	return 0;
}

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