剑指Offer45 约瑟夫环

/*************************************************************************
    > File Name: 45_LastNumberInCircle.cpp
    > Author: Juntaran
    > Mail: JuntaranMail@gmail.com
    > Created Time: 2016年09月04日 星期日 20时21分57秒
 ************************************************************************/
 
#include <stdio.h>
#include <bits/stdc++.h>

using namespace std;


// 环形链表
int LastRemaining1(int n, int m)
{
    if (n<1 || m<1)
        return -1;
    
    int i = 0;
    
    list<int> numbers;
    for (int i = 0; i < n; ++i)
        numbers.push_back(i);
    
    list<int>::iterator current = numbers.begin();
    while (numbers.size() > 1)
    {
        for (int i = 1; i < m; ++i)
        {
            current ++;
            if (current == numbers.end())
                current = numbers.begin();
        }
        list<int>::iterator next = ++current;
        if (next == numbers.end())
            next = numbers.begin();
        
        --current;
        numbers.erase(current);
        current = next;
    }
    return *current;
}

// 数组模拟环
int LastRemaining2(int n, int m)
{
    if (n<1 || m<1)
        return -1;
    
    int array[n];
    int i = -1;
    int step = 0;
    int count = n;
    
    while (count > 0)
    {
        i ++;
        if (i >= n)            // 模拟环
            i = 0;
        if (array[i] == -1)
            continue;
        step ++;
        if (step == m)
        {
            array[i] = -1;
            step = 0;
            count --;
        }
    }
    int ret = i;
    return ret;
}

// 数学解法
int LastRemaining3(int n, int m)
{
    if (n<1 || m<1)
        return -1;
    
    int ret = 0;
    for (int i = 2; i <= n; ++i)
        ret = (ret + m) % i;
    
    return ret;
}

int main()
{
    int n = 100;
    int m = 5;
    
    int ret1 = LastRemaining1(n, m);
    int ret2 = LastRemaining2(n, m);
    int ret3 = LastRemaining3(n, m);
    
    printf("ret1 is %d
", ret1);
    printf("ret2 is %d
", ret2);
    printf("ret3 is %d
", ret3);
    
    return 0;
}