#include <iostream>
#include <queue>
#include <cctype>
#include <map>

struct Coor 
{ 
	int x; int y; int t;
	Coor(int in_x, int in_y, int in_t) :
		x(in_x), y(in_y), t(in_t)
	{}
	Coor() :
		x(0), y(0), t(0)
	{}
	bool operator==(const Coor& another) const { return x == another.x && y == another.y; }
	Coor& operator=(const Coor& another) { x = another.x; y = another.y; return *this; }
};

int N, M;
char mapArr[301][301];
bool boolArr[301][301];
std::queue<Coor> coorQueue;
std::map<char, std::pair<Coor, Coor>> specialMap; //装置对

int run()
{
	while (mapArr[coorQueue.front().x][coorQueue.front().y] != '=')
	{
		boolArr[coorQueue.front().x][coorQueue.front().y] = true;
		if (isalpha(mapArr[coorQueue.front().x][coorQueue.front().y]))
		{
			const std::pair<Coor, Coor>& curPair = specialMap[mapArr[coorQueue.front().x][coorQueue.front().y]];
			if (curPair.first == coorQueue.front())
			{
				coorQueue.front() = curPair.second;
			}
			else
			{
				coorQueue.front() = curPair.first;
			}
		}
		int nextX = coorQueue.front().x + 1, nextY = coorQueue.front().y;
		if (mapArr[nextX][nextY] != '#' && !boolArr[nextX][nextY])
		{
			coorQueue.push(Coor(nextX, nextY, coorQueue.front().t + 1));
		}
		nextX = coorQueue.front().x - 1, nextY = coorQueue.front().y;
		if (mapArr[nextX][nextY] != '#' && !boolArr[nextX][nextY])
		{
			coorQueue.push(Coor(nextX, nextY, coorQueue.front().t + 1));
		}
		nextX = coorQueue.front().x, nextY = coorQueue.front().y + 1;
		if (mapArr[nextX][nextY] != '#' && !boolArr[nextX][nextY])
		{
			coorQueue.push(Coor(nextX, nextY, coorQueue.front().t + 1));
		}
		nextX = coorQueue.front().x, nextY = coorQueue.front().y - 1;
		if (mapArr[nextX][nextY] != '#' && !boolArr[nextX][nextY])
		{
			coorQueue.push(Coor(nextX, nextY, coorQueue.front().t + 1));
		}
		coorQueue.pop();
	}
	return coorQueue.front().t;
}

int main()
{
	std::cin >> N >> M;
	for (int _i = 0; _i < N; ++_i)
	{
		for (int _j = 0; _j < M; ++_j)
		{
			std::cin >> mapArr[_i][_j];
			if (isalpha(mapArr[_i][_j]))
			{
				std::pair<Coor, Coor>& curPair = specialMap[mapArr[_i][_j]];
				if (curPair.first.x)
				{
					curPair.second.x = _i; curPair.second.y = _j;
				}
				else
				{
					curPair.first.x = _i; curPair.first.y = _j;
				}
			}
			else if (mapArr[_i][_j] == '@')
			{
				coorQueue.push(Coor(_i, _j, 0));
			}
		}
	}
	//删除不成对的装置，将其置为#
	for (std::map<char, std::pair<Coor, Coor>>::iterator it = specialMap.begin(); it != specialMap.end(); ++it)
	{
		if (!it->second.second.x)
		{
			mapArr[it->second.first.x][it->second.first.y] = '#';
			it = specialMap.erase(it);
		}
	}
	std::cout << run();
}

提交结果 3 6 13 15 16都tle了。

顺便问下，为何我一个测试点都下载不了呀？