poj 1154 LETTERS(深搜)

最新推荐文章于 2024-03-16 21:55:17 发布

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本文介绍了一款单人棋盘游戏的最优路径搜索算法。游戏在一个包含大写字母的R行C列的矩形棋盘上进行，玩家需控制棋子在不同字母格间移动，且不允许重复进入相同字母的格子。文章提供了一个深度优先搜索算法实现，通过递归地探索所有可能路径来找出棋子能访问的最大格子数。

LETTERS

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 8844		Accepted: 3962

Description

A single-player game is played on a rectangular board divided in R rows and C columns. There is a single uppercase letter (A-Z) written in every position in the board.
Before the begging of the game there is a figure in the upper-left corner of the board (first row, first column). In every move, a player can move the figure to the one of the adjacent positions (up, down,left or right). Only constraint is that a figure cannot visit a position marked with the same letter twice.
The goal of the game is to play as many moves as possible.
Write a program that will calculate the maximal number of positions in the board the figure can visit in a single game.

Input

The first line of the input contains two integers R and C, separated by a single blank character, 1 <= R, S <= 20.
The following R lines contain S characters each. Each line represents one row in the board.

Output

The first and only line of the output should contain the maximal number of position in the board the figure can visit.

Sample Input

3 6
HFDFFB
AJHGDH
DGAGEH

Sample Output

tips:注意book数组的使用方式，简单深搜

#include<iostream>
#include<cstring>
#include<queue>
using namespace std;

char mapp[22][22];
int n,m;

int book[122];
int dire[4][2]={-1,0,1,0,0,-1,0,1};
int ans;

void dfs(int x,int y,int step)
{
	ans=max(ans,step);
	
	for(int i=0;i<4;i++)
	{
			int nx=dire[i][0]+x;
			int ny=dire[i][1]+y;
			if(nx<=0||nx>n||ny<=0||ny>m)continue;
			if(!book[mapp[nx][ny]]){
				book[mapp[nx][ny]]++;
				dfs(nx,ny,step+1); 
				book[mapp[nx][ny]]--;
			} 
	}
}
int main()
{
	cin>>n>>m;
	getchar();
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			cin>>mapp[i][j];
		}
		getchar();
	}
	book[mapp[1][1]]++;
	dfs(1,1,1);
	
	cout<<ans<<endl;
	return 0;
}