CodeForces Gym 100735C BFS

最新推荐文章于 2020-11-03 21:06:59 发布

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本文介绍了一种基于广度优先搜索(BFS)的迷宫寻宝游戏算法。该算法通过记录玩家(A)与卫士(G)的位置状态，判断玩家是否能在被卫士捕获前取得护身符(P)。

就是一个迷宫，然后A可以自己选择去走，但是卫士在A走后会根据A的位置去走，问A能不能拿到那个护身符，假如A拿到后下一步就被卫士干死，也是认为他不能拿到的

就BFS让A走，然后卫士就根据A去模拟就行，状态记录就是walk[ra][ca][rg][cg]，表示 A和卫士各自在的位置，然后就BFS跑就行，只是挺烦的，就错了一个地方，&&改成||就能AC，然后以为自己错误很多就没去查，，，，简直智障

#include <cstdio>
#include <cstring>
#include <vector>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
using namespace std;
const int dx[4] = { -1, 1, 0, 0 };//上下左右
const int dy[4] = { 0, 0, -1, 1 };
struct Node
{
	int ra, ca, rg, cg, cnt;
	Node() : ra(0), ca(0), rg(0), cg(0), cnt(0) {}
	Node(int ra, int ca, int rg, int cg, int cnt)
	{
		this->ra = ra; this->ca = ca;
		this->rg = rg; this->cg = cg;
		this->cnt = cnt;
	}
};
int N, M;
char grid[30][30];
bool walk[30][30][30][30];
int main()
{
	//freopen("input.txt", "r", stdin);
	scanf("%d%d", &N, &M);
	for (int i = 0; i < N; ++i)
		scanf("%s", grid[i]);
	Node st;
	for (int i = 0; i < N; ++i)
	{
		for (int j = 0; j < M; ++j)
		{
			if (grid[i][j] == 'A')
			{
				st.ra = i; st.ca = j;
				grid[i][j] = '.';
			}
			else if (grid[i][j] == 'G')
			{
				st.rg = i; st.cg = j;
				grid[i][j] = '.';
			}
		}
	}
	st.cnt = 0;
	/*printf("N %d M %d\n", N, M);
	for (int i = 0; i < N; ++i)
		printf("%s\n", grid[i]);*/
	//printf("ra %d ca %d rg %d cg %d\n", st.ra, st.ca, st.rg, st.cg);
	walk[st.ra][st.ca][st.rg][st.cg] = true;
	queue<Node> Q;
	Q.push(st);
	Node t;
	int r1, c1, r2, c2;
	int ans = -1;
	while (!Q.empty())
	{
		t = Q.front();
		Q.pop();
		if (grid[t.ra][t.ca] == 'P')
		{
			ans = t.cnt;
			break;
		}
		for (int i = 0; i < 4; ++i)
		{
			r1 = t.ra + dx[i];
			c1 = t.ca + dy[i];
			//printf("a %d %d  %c\n", r1, c1, grid[r1][c1]);
			//printf("rg %d cg %d\n", t.rg, t.cg);
			if (r1 >= 0 && r1 < N&&c1 >= 0 && c1 < M&&grid[r1][c1] != 'X' && (r1 != t.rg || c1 != t.cg))
			{
				//printf("a go %d %d\n", r1, c1);
				bool guard = false;
				if (t.cg < c1)
				{
					c2 = t.cg + 1; r2 = t.rg;
					if (c2 == c1&&r2 == r1)
						continue;
					if (grid[r2][c2] != 'X')
					{
						guard = true;
					}
				}
				else if (t.cg > c1)
				{
					c2 = t.cg - 1; r2 = t.rg;
					if (c2 == c1&&r2 == r1)
						continue;
					if (grid[r2][c2] != 'X')
					{
						guard = true;
					}
				}
				if (!guard)
				{
					if (t.rg < r1)
					{
						r2 = t.rg + 1; c2 = t.cg;
						if (c2 == c1&&r2 == r1)
							continue;
						if (grid[r2][c2] != 'X')
						{
							guard = true;
						}
					}
					else if (t.rg>r1)
					{
						r2 = t.rg - 1; c2 = t.cg;
						if (c2 == c1&&r2 == r1)
							continue;
						if (grid[r2][c2] != 'X')
						{
							guard = true;
						}
					}
				}
				if (guard == false)//guard下一步是野兽，所以不能走
				{
					r2 = t.rg; c2 = t.cg;
				}
				if (!walk[r1][c1][r2][c2])
				{
					//printf("%d %d %d %d\n", r1, c1, r2, c2);
					Q.push(Node(r1, c1, r2, c2, t.cnt + 1));
					walk[r1][c1][r2][c2] = true;
				}
			}
		}
		if (ans > -1)
			break;
	}
	printf("%d\n", ans);
	//system("pause");
	//while (1);
	return 0;
}