约瑟夫环问题
直接上C++代码：
这里有问题的地方就是joseph_circle.cpp实现方法eliminate的循环语句的条件，如果把p->next != p改为p->next != nullptr就会出现循环已经删除了最后一个还继续循环，还继续删除，然后抛出空指针异常。
joseph_circle.h
1 #ifndef __YueHeFuHuan__joseph_circle__ 2 #define __YueHeFuHuan__joseph_circle__ 3 4 #include <stdio.h> 5 #include <iostream> 6 using namespace std; 7 struct node{ 8 int payload; 9 node* next; 10 node(int value){ 11 payload = value; 12 }//通过构造器传值更好，更直观。 13 }; 14 15 class joseph_circle{ 16 public: 17 joseph_circle(); 18 node* tail; 19 void add(int n); 20 void output(); 21 void eliminate(int step); 22 }; 23 24 25 #endif /* defined(__YueHeFuHuan__joseph_circle__) */
joseph_circle.cpp
1 #include "joseph_circle.h" 2 3 joseph_circle::joseph_circle(){ 4 tail = nullptr; 5 } 6 void joseph_circle::add(int value){ 7 if (tail == nullptr) { 8 tail = new node(value); 9 tail->next = tail; 10 }else{ 11 node* next_node = tail->next; 12 tail->next = new node(value); 13 tail = tail->next; 14 tail -> next = next_node; 15 16 } 17 } 18 void joseph_circle::output(){ 19 if (tail == nullptr) { 20 cout << "链表为空！" << endl; 21 }else{ 22 node* p = tail->next; 23 while (true) { 24 cout << "payload:" << p->payload << endl; 25 if (p == tail) { 26 break; 27 } 28 p = p->next; 29 } 30 } 31 } 32 void joseph_circle::eliminate(int step){ 33 if (tail == nullptr) { 34 cout << "链表为空！" << endl; 35 }else{ 36 node* p = tail; 37 node* delete_p; 38 //事实证明，当delete一个指针之后，其指针指向不为空 39 while (p != nullptr && p->next != p) { 40 //根据步长找到目标元素 41 for (int i=0; i<step-1; i++) { 42 p = p->next; 43 } 44 delete_p = p->next; 45 cout << "deleting: " << delete_p->payload << endl; 46 p->next = delete_p->next; 47 if (delete_p == tail) { 48 tail = p; 49 } 50 delete delete_p; 51 52 } 53 } 54 }
