BFS——最小步数 续

上一次用的DFS，这次BFS，直接在地图上扩展结点，如下图所示：

橙黄色代表起点，浅蓝色终点。

---

#include <cstdio>
#include <queue>

using namespace std;

#define ACCESS      0

struct position
{
	int x, y;
}start, end;

const int direction[4][2] = {-1, 0, 0, 1, 1, 0, 0, -1};

queue<position> toExpandPosition;

void BFSExploreMaze(int &minStep)
{
	int i;
	int mazeMap[9][9] =
	{
		1,1,1,1,1,1,1,1,1,
		1,0,0,1,0,0,1,0,1,
		1,0,0,1,1,0,0,0,1,
		1,0,1,0,1,1,0,1,1,
		1,0,0,0,0,1,0,0,1,
		1,1,0,1,0,1,0,0,1,
		1,1,0,1,0,1,0,0,1,
		1,1,0,1,0,0,0,0,1,
		1,1,1,1,1,1,1,1,1
	};
	position currentPos, adjacentPos;
	while (!toExpandPosition.empty())
	{
		toExpandPosition.pop();
	}
	toExpandPosition.push(start);

	while (!toExpandPosition.empty())
	{
		currentPos = toExpandPosition.front();
		toExpandPosition.pop();
		if (currentPos.x == end.x && currentPos.y == end.y)
		{
			minStep = mazeMap[currentPos.x][currentPos.y];
			return;
		}
		for (i = 0; i < 4; i++)
		{
			adjacentPos.x = currentPos.x + direction[i][0];
			adjacentPos.y = currentPos.y + direction[i][1];
			if (mazeMap[adjacentPos.x][adjacentPos.y] == ACCESS)
			{
				mazeMap[adjacentPos.x][adjacentPos.y] =
					mazeMap[currentPos.x][currentPos.y] + 1;
				toExpandPosition.push(adjacentPos);
			}
		}
	}
}

int main()
{
	int testNum, minStep;
	scanf("%d", &testNum);
	while (testNum-- != 0)
	{
		scanf("%d%d%d%d", &start.x, &start.y, &end.x, &end.y);
		BFSExploreMaze(minStep);
		printf("%d\n", minStep);
	}
	return 0;
}