Robot
Time Limit: 8000/4000 MS (Java/Others) Memory Limit: 102400/102400 K (Java/Others)
Total Submission(s): 158 Accepted Submission(s): 46
Problem Description
Michael has a telecontrol robot. One day he put the robot on a loop with n cells. The cells are numbered from 1 to n clockwise.
At first the robot is in cell 1. Then Michael uses a remote control to send m commands to the robot. A command will make the robot walk some distance. Unfortunately the direction part on the remote control is broken, so for every command the robot will chose a direction(clockwise or anticlockwise) randomly with equal possibility, and then walk w cells forward.
Michael wants to know the possibility of the robot stopping in the cell that cell number >= l and <= r after m commands.
At first the robot is in cell 1. Then Michael uses a remote control to send m commands to the robot. A command will make the robot walk some distance. Unfortunately the direction part on the remote control is broken, so for every command the robot will chose a direction(clockwise or anticlockwise) randomly with equal possibility, and then walk w cells forward.
Michael wants to know the possibility of the robot stopping in the cell that cell number >= l and <= r after m commands.
Input
There are multiple test cases.
Each test case contains several lines.
The first line contains four integers: above mentioned n(1≤n≤200) ,m(0≤m≤1,000,000),l,r(1≤l≤r≤n).
Then m lines follow, each representing a command. A command is a integer w(1≤w≤100) representing the cell length the robot will walk for this command.
The input end with n=0,m=0,l=0,r=0. You should not process this test case.
Each test case contains several lines.
The first line contains four integers: above mentioned n(1≤n≤200) ,m(0≤m≤1,000,000),l,r(1≤l≤r≤n).
Then m lines follow, each representing a command. A command is a integer w(1≤w≤100) representing the cell length the robot will walk for this command.
The input end with n=0,m=0,l=0,r=0. You should not process this test case.
Output
For each test case in the input, you should output a line with the expected possibility. Output should be round to 4 digits after decimal points.
Sample Input
3 1 1 2
1
5 2 4 4
1
2
0 0 0 0
Sample Output
0.5000
0.2500
Source
按照概率DP过去，比较暴力，T_T
1 /* ********************************************** 2 Author : kuangbin 3 Created Time: 2013/8/10 11:51:05 4 File Name : F:2013ACM练习比赛练习2013杭州邀请赛重现1001.cpp 5 *********************************************** */ 6 7 #include <stdio.h> 8 #include <string.h> 9 #include <iostream> 10 #include <algorithm> 11 #include <vector> 12 #include <queue> 13 #include <set> 14 #include <map> 15 #include <string> 16 #include <math.h> 17 #include <stdlib.h> 18 using namespace std; 19 double dp[2][220]; 20 int main() 21 { 22 //freopen("in.txt","r",stdin); 23 //freopen("out.txt","w",stdout); 24 int n,m,l,r; 25 while(scanf("%d%d%d%d",&n,&m,&l,&r) == 4) 26 { 27 if(n == 0 && m == 0 && l == 0 && r == 0)break; 28 dp[0][0] = 1; 29 for(int i = 1;i < n;i++)dp[0][i] = 0; 30 int now = 0; 31 while(m--) 32 { 33 int v; 34 scanf("%d",&v); 35 for(int i = 0;i < n;i++) 36 dp[now^1][i] = 0.5*dp[now][(i-v+n)%n] + 0.5*dp[now][(i+v)%n]; 37 now ^= 1; 38 } 39 double ans = 0; 40 for(int i = l-1;i < r;i++) 41 ans += dp[now][i]; 42 printf("%.4lf ",ans); 43 } 44 return 0; 45 }