ZOJ2271 Chance to Encounter a Girl

来源：互联网发布：数据分析公司统计学编辑：程序博客网时间：2024/06/07 02:00

入门级DP题，最重要就是每天更新每个格子的小女孩出现的概率，同时累加年轻人所在格子的小女孩出现的概率后清零

/******************************************************************************* # Author : Neo Fung # Email : neosfung@gmail.com # Last modified: 2011-12-30 19:19 # Filename: ZOJ2271 Chance to Encounter a Girl.cpp # Description :  ******************************************************************************/// #include "stdafx.h"// #define DEBUG#include <fstream>#include <stdio.h>#include <iostream>#include <string.h>#include <string>#include <memory.h>#include <limits.h>#include <algorithm>#include <math.h>#include <numeric>#include <functional>#include <ctype.h>#defineMAX 120using namespace std;double dp[MAX][MAX],pre[MAX][MAX];int check(const int &x,const int &y,const int &n){int ans=0;if(x+1<n)++ans;if(x>0)++ans;if(y+1<n)++ans;if(y>0)++ans;return ans;}void travel(const int &n){memset(dp,0.0,sizeof(dp));for(int i=0;i<n;++i)for(int j=0;j<n;++j)if(pre[i][j]>0.0){double temp=pre[i][j]/check(i,j,n);if(i+1<n)dp[i+1][j]+=temp;if(i>0)dp[i-1][j]+=temp;if(j+1<n)dp[i][j+1]+=temp;if(j>0)dp[i][j-1]+=temp;}memcpy(pre,dp,sizeof(dp));}int main(void){#ifdef DEBUG    freopen("C:/Users/neo/Desktop/stdin.txt","r",stdin);  freopen("C:/Users/neo/Desktop/stdout.txt","w",stdout); #endif  int n;while(~scanf("%d",&n)){memset(pre,0.0,sizeof(pre));pre[n/2][n/2]=1;double ans=0.0;for(int i=0;i<n;++i){travel(n);ans+=pre[i][n/2];pre[i][n/2]=0.0;}printf("%.4lf\n",ans);}  return 0;}