hdoj 2407 Knots
来源:互联网 发布:知乎怎么添加关注话题 编辑:程序博客网 时间:2024/05/22 03:47
Knots
Time Limit: 1000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 253 Accepted Submission(s): 176
Problem Description
An even number N of strands are stuck through a wall. On one side of the wall, a girl ties N/2 knots between disjoint pairs of strands. On the other side of the wall, the girl's groom-to-be also ties N/2 knots between disjoint pairs of strands. You are to find the probability that the knotted strands form one big loop (in which case the couple will be allowed to marry).
For example, suppose that N = 4 and you number the strands 1, 2, 3, 4. Also suppose that the girl has created the following pairs of strands by tying knots: {(1, 4), (2,3)}. Then the groom-to-be has two choices for tying the knots on his side: {(1,2), {3,4)} or {(1,3), (2,4)}.
For example, suppose that N = 4 and you number the strands 1, 2, 3, 4. Also suppose that the girl has created the following pairs of strands by tying knots: {(1, 4), (2,3)}. Then the groom-to-be has two choices for tying the knots on his side: {(1,2), {3,4)} or {(1,3), (2,4)}.
Input
The input file consists of one or more lines. Each line of the input file contains a positive even integer, less than or equal to 100. This integer represents the number of strands in the wall.
Output
For each line of input, the program will produce exactly one line of output: the probability that the knotted strands form one big loop, given the number of strands on the corresponding line of input. Print the probability to 5 decimal places.
Sample Input
420
Sample Output
0.666670.28377
公式:((n-2)*(n-4)*(n-6)*...)/((n-1)*(n-3)*(n-5)*...)
代码:
#include<stdio.h> #include<stdlib.h> #include<string.h> #include<algorithm>using namespace std;#define INF 0x3f3f3fint main(){int n,i;double a[105];a[2]=1.0;for(i=4;i<=105;i+=2){a[i]=a[i-2]*(i-2)/(i-1);}while(scanf("%d",&n)!=EOF)printf("%.5lf\n",a[n]);return 0;}
0 0
- hdoj 2407 Knots
- hdoj--2407--Knots(规律题)
- HDOJ 2407 Knots(递推规律题)
- ♥HDOJ 2407-Knots【大爷的规律题】
- Hdu 2407 Knots【概率】
- Knots 2407 (规律题)
- Knots UVA
- HUST 1176 Knots
- Knots (组合数学)
- HDOJ
- hdoj
- hdoj
- HDOJ
- hdoj 1568 && hdoj 5344 && hdoj 5444
- HDOJ 2176
- Hdoj--1272
- hdoj 1003
- hdoj 1005
- bfs
- 6_Linux系统中的进程创建分析
- 第五周项目三-时间类(1)
- 【VIP】【图】332. Reconstruct Itinerary【M】【47】
- 良好使用UIView,使自定义的视图低耦合、高内聚
- hdoj 2407 Knots
- Spring-理解AOP
- 图示经典算法--快速排序
- 一次意外的ioctl调用错误—论不同版本内核的ioctl函数实现
- N
- 自学
- Trick(十六)—— 随机数的生成
- uestc1135邱老师看电影【概率dp】
- Java多线程详解