N 人报数,最后只剩一人问题

/*** 现有N个人绕着一个足够大的园桌按顺时针坐成一圈, 每个人都有一个编号,编号从0开始,* 从0号的人开始按顺时针报数,报的数从1开始, 凡是报的数字是7的倍数,或数字中有7, 这个人就从桌子上离开,* 按顺时针方向后面的人继续进行报数.依此进行下去,最终桌上会剩下的最后一个人,问最后剩下的这个人的编号是几？* 请编写一个C程序解决.如果用C++语言, 你又如何解决?***/#include "timer.h"#include <stdio.h>#include <string>#include <cstddef>#include <assert.h>#include <iostream>#include <exception>#include <stdexcept>class Element{public:    unsigned long _data;    Element* _pre;    Element* _next;    Element() : _pre ( NULL ), _next ( NULL ), _data ( 0 ) {}};Element*  CreatCircularList ( unsigned long N );bool DeleteElementList ( Element *p );/** N 个数，数到的数是base的整数倍，或是此数里含有base，就移除*/// 为了降低难度，此处假设base 是7, pHead 是包含 N个元素的循环链表void Detect7 ( Element* pHead, unsigned long base );//判断num中是否存在 7， true, existbool CheckSeven ( unsigned long  num );Element* gRelease = NULL;int main ( int argc, char **argv ){    unsigned long  N;    printf ( "How long do you want? please enter a positive number: " );    scanf ( "%d", &N );    gRelease = new Element;    assert ( gRelease );    Element* pHead = CreatCircularList ( N );    assert ( pHead );    // init the list    for ( int i = 0; i != N ; ++i ) {        pHead->_data = i;        pHead = pHead->_next;    }    TimeStart();    Detect7 ( pHead, 7 );    TimeStop();    printf ( "process time is : %f us \n", GetElapsedTime() );    DeleteElementList ( gRelease );#ifdef _WIN32    system ( "pause" );#endif}Element*  CreatCircularList ( unsigned long  N ){    assert ( N > 0 );    TimeStart();    Element *head = new Element;    assert ( head != NULL );    Element *cur = NULL;    cur = head;    try {        for ( unsigned long  i = 0; i != N - 1; ++i ) {            //            Element * temp = new Element;            assert ( temp != NULL );            temp->_pre = cur;                   // temp point to previous            cur->_next = temp;                  // previous point to temp            cur = cur->_next;        }        cur->_next = head; // circular linked list        head->_pre = cur;    } catch ( const std::bad_alloc& err ) {        printf ( "%s \n", err.what() );        return NULL;    }    TimeStop();    printf ( "Allocate memory time is : %f us \n", GetElapsedTime() );    return head;}// release Element Listbool DeleteElementList ( Element *p ){    assert ( p != NULL );    Element * rel = p;    // int num = 0;    while ( rel->_next ) {        Element * temp = rel;        rel = rel->_next;        delete temp;        //++num;    }    delete rel;    // printf ( "内存释放 %d  次\n", num );    return true;}void Detect7 ( Element* pHead, unsigned long base ){    assert ( pHead > 0 );    assert ( base > 0 );    Element* pRelease = gRelease;    Element* pCurrent = pHead;    for ( unsigned long  i = 1;; ++i ) {        if ( i == -1 ) {            printf ( "over flow \n" );            return;        }        if ( pCurrent->_data == pCurrent->_next->_data ) {//判断是否是最后一个元素            printf ( "The last member is %d \n", pCurrent->_data );            //for release            pRelease->_next = pCurrent;            pRelease = pRelease->_next;            pRelease->_next = NULL;            return;        }        if ( i % 7 == 0 ) { //判断是否是7 的倍数            pCurrent->_pre->_next = pCurrent->_next;            pCurrent->_next->_pre = pCurrent->_pre;            //for release            pRelease->_next = pCurrent;            pRelease = pRelease->_next;            pCurrent = pCurrent->_next;            continue;        }        if ( CheckSeven ( i ) ) { //判断是否包含7            pCurrent->_pre->_next = pCurrent->_next;            pCurrent->_next->_pre = pCurrent->_pre;            //for release            pRelease->_next = pCurrent;            pRelease = pRelease->_next;            pCurrent = pCurrent->_next;            continue;        }        pCurrent = pCurrent->_next;    }    return;}//判断num中是否存在 7， true, existbool CheckSeven ( unsigned long  num ){    if ( num <= 0 ) return false;    unsigned long  ret = num;    unsigned long  remainder = 0;    remainder = ret % 10; //求个位上的数字是几    if ( remainder == 7 )        return true;    else        CheckSeven ( num / 10 );}

#include "timer.h"i64 time_start ;i64 time_stop ;i64 time_freq ;void TimeStart(){#if _WIN32    QueryPerformanceFrequency ( ( LARGE_INTEGER * ) &time_freq );    QueryPerformanceCounter ( ( LARGE_INTEGER * ) &time_start );#elif __linux__    time_freq = 1000;    struct timeval s;    gettimeofday ( &s, 0 );    time_start = ( i64 ) s.tv_sec * 1000 + ( i64 ) s.tv_usec / 1000;#endif}void TimeStop(){#if _WIN32    QueryPerformanceCounter ( ( LARGE_INTEGER * ) &time_stop );#elif __linux__    struct timeval s;    gettimeofday ( &s, 0 );    time_stop = ( i64 ) s.tv_sec * 1000 + ( i64 ) s.tv_usec / 1000;#endif    time_stop -= time_start;}double GetElapsedTime(){    // unit: us    return ( double ) time_stop * 1000000 / ( double ) time_freq;}