問題：

有n個人圍成一圈，按順序從1到n編好號。從第一個人開始報數，報到3的人退出圈子，下一個人從1開始報數，報到3的人退出圈子。如此下去，直到留下最後一個人。請按退出順序輸出退出圈子的人的編號

思路：

用資料結構中的迴圈連結串列解決此題

程式碼：

#include<stdio.h>
#include <stdlib.h>
typedef struct node {
    int num;
    struct node* next;
}Node,*PNode;
typedef struct point {
    PNode head;
    PNode tail;
}Point;
void init(Point* p) {
    p->head = (PNode)malloc(sizeof(Node));
    p->tail = p->head;
    printf
 
("input the num of people\n");
    int pNum;
    scanf("%d", &pNum);
    for ( int i = 0; i < pNum; i++)
    {
        PNode tPoint= (PNode)malloc(sizeof(Node));

        p->tail->next = tPoint;
        p->tail = tPoint;
        p->tail->num = i+1;

    }
    p->tail->next
 
 = p->head->next;
}
int counting(Point* p) {
    int count = 0;
    PNode pNow = p->head;
    while(pNow->next != pNow){
        pNow = pNow->next;
        count++;
        if (count==2) {
            PNode pTemp = pNow->next;
            pNow->next = pNow->next->next;
            free(pTemp);
            count = 1
 
;
            pNow = pNow->next;
        }


    }
    return pNow->num;

}
void print(Point* p) { //test
    PNode pNow = p->head;
    pNow = pNow->next;
    do{
        printf("%d\n", pNow->num);
        pNow = pNow->next;

    }while (pNow->next != p->head->next);

}
int main()
{ 
    Point p;
    init(&p);
//  print(&p);
    int count = counting(&p);
    printf("the last people is %dth", count);
    return 0;
}