LightOJ - 1179 Josephus Problem(约瑟夫)

最新推荐文章于 2021-11-19 16:33:28 发布

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原文链接：http://www.cnblogs.com/soTired/p/5333149.html

本文探讨了约瑟夫环问题的历史背景及算法实现。通过两种不同的编程方式解决了该问题：一种是递推方法，另一种是模拟过程。递推方法通过预计算的方式找到最后幸存者的初始位置；而模拟过程则通过不断移除被选中的人来确定最终结果。

Josephus Problem

Time Limit: 2000MS

Memory Limit: 32768KB

64bit IO Format: %lld & %llu

Submit Status

Description

The historian Flavius Josephus relates how, in the Romano-Jewish conflict of 67 A.D., the Romans took the town of Jotapata which he was commanding. Escaping, Josephus found himself trapped in a cave with 40 companions. The Romans discovered his whereabouts and invited him to surrender, but his companions refused to allow him to do so. He therefore suggested that they kill each other, one by one, the order to be decided by lot. Tradition has it that the means for affecting the lot was to stand in a circle, and, beginning at some point, count round, every third person being killed in turn. The sole survivor of this process was Josephus, who then surrendered to the Romans. Which begs the question: had Josephus previously practiced quietly with 41 stones in a dark corner, or had he calculated mathematically that he should adopt the 31^st position in order to survive?

Now you are in a similar situation. There are n persons standing in a circle. The persons are numbered from 1 to n circularly. For example, 1 and n are adjacent and 1 and 2 are also. The count starts from the first person. Each time you count up to k and the k^th person is killed and removed from the circle. Then the count starts from the next person. Finally one person remains. Given n and k you have to find the position of the last person who remains alive.

Input

Input starts with an integer T (≤ 200), denoting the number of test cases.

Each case contains two positive integers n (1 ≤ n ≤ 10⁵) and k (1 ≤ k < 2³¹).

Output

For each case, print the case number and the position of the last remaining person.

Sample Input

2 1

2 2

3 1

3 2

3 3

4 6

Sample Output

Case 1: 2

Case 2: 1

Case 3: 3

Case 4: 3

Case 5: 2

Case 6: 3

Source

Problem Setter: Jane Alam Jan

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#include <cstdio>
#define N 100010
int rec[N];
int deal(int n, int k)
{
    rec[1]=0;
    for(int i=2; i<=n; i++)
        rec[i]=(rec[i-1]+k)%i;
    return rec[n]+1;
}
int main()
{
    int t;  int Q=1;
    scanf("%d", &t);
    while(t--)
    {
        int n, k; scanf("%d%d", &n, &k);
        printf("Case %d: %d\n", Q++, deal(n, k));
    }
    return 0;
}

暴力码，超时 ;

#include <cstdio>
#include <cstring>
#define N 100001
int ps[N], v[N];
using namespace std;
int deal(int n, int k)
{
    int rec, times=0, cnt=0, sumP=0;
    for(int i=1; i<=n; i++)
    {
        if(!v[i]) cnt++; 
        if(cnt==k)
        {
            v[i]=1;
            cnt=0;
            sumP++;
            rec=i;
        }
        if(i==n) i=0;
        if(sumP==n) break;
    }
    return rec;
}
int main()
{
    int T; int Q=1; 
    scanf("%d", &T);
    while(T--)
    {
        int n, k; memset (v, 0, sizeof(v));
        scanf("%d%d", &n, &k);
        printf("Case %d: %d\n", Q++,  deal(n, k));  
    }
    return 0;
}