注:此篇是我使用指针敲的一些题目的集成，有一些代码是重复的(挠头)。这样做的目的是进行前后的一些比较和收获一些心得(?)。
关于上一次我上台的题目:
题目:输入十个整数，进行排序。
做法1:(传递指针p)
#include#include #include using namespace std;void swap(int *p){ int i,j; int t; for(i = 1 ; i <= 10; i++) { for(j = i + 1; j <= 10; j++) { if(*(p + j) < *(p + i)) { t = *(p + i); *(p + i) = *(p + j); *(p + j) = t; } } } for(i = 1; i <= 10; i++) { printf("%d ",*(p + i)); } printf("\n");}int main(){ int a[10]; memset(a,0,sizeof(a)); int i,j; int *p; p = a; for(i = 1; i <= 10; i++) { scanf("%d",&a[i]); } swap(p); return 0;}
做法2:(传递数组名)
#include#include #include using namespace std;void swap(int a[]){ int i,j; int t; for(i = 1 ; i <= 10; i++) { for(j = i + 1; j <= 10; j++) { if(a[j] < a[i]) { t = a[i]; a[i] = a[j]; a[j] = t; } } } for(i = 1; i <= 10; i++) { printf("%d ",a[i]); } printf("\n");}int main(){ int a[10]; memset(a,0,sizeof(a)); int i,j; for(i = 1; i <= 10; i++) { scanf("%d",&a[i]); } swap(a); return 0;}
链表
有段时间没敲链表了(挠头)，重新实现下，发现还是很多地方出错了:(
经过漫长时间的debug，发现一个原因是，在主函数里面定义的整形变量，在函数pdelete里面缺少了对其的定义，编译居然过了(挠头) 写了两遍。贴个最后一次实现的代码吧。
链表的创建，输出，插入和删除
#include#include #include using namespace std;struct Node{ int data; Node *next;};void IniNode(Node *head){ head = (Node *)malloc(sizeof(Node)); if(head == NULL) { printf("Overflow\n"); exit(1); } head -> next = NULL; head -> data = -1;}Node *Creat(){ Node *head; IniNode(head); Node *p1,*p2; p1 = p2 = head; while(p1 -> next != NULL || p1 == head) { int a = 0; scanf("%d",&a); if(a < 0) { p1 -> next = NULL; break; } p1 = (Node *)malloc(sizeof(Node)); if(p1 == NULL) { printf("Overflow\n"); exit(1); } p1 -> data = a; p2 -> next = p1; p2 = p1; } return head;}void output(Node *head){ Node *p = head -> next; while(p != NULL) { printf("%d ",p -> data); p = p -> next; } printf("\n");}void pinsert(Node *head){ Node *p1,*p2; p1 = p2 = head; int i_data = 0,num = 0; scanf("%d%d",&num,&i_data); int i,j; for(i = 1; i <= num; i++) { p2 = p1; p1 = p1 -> next; } Node *p; p = (Node *)malloc(sizeof(Node)); if(p == NULL) { printf("Overflow\n"); exit(1); } p -> next = p1; p -> data = i_data; p2 -> next = p; output(head);}void pdelete(Node *head){ Node *p1,*p2; p1 = p2 = head; int d_num = 0; scanf("%d",&d_num); int i,j; for(i = 1; i <= d_num; i++) { p2 = p1; p1 = p1 -> next; } p1 = p1 -> next; free(p2 -> next); // 勿忘我 p2 -> next = p1; output(head);}int main(){ Node *head; head = Creat(); output(head); pinsert(head); pdelete(head); return 0;}
链表错误小结
- 构建部分:
void IniNode(Node *head){ head = (Node *)malloc(sizeof(Node)); if(head == NULL) { printf("Overflow\n"); exit(1); } head -> next = NULL; head -> data = -1;}Node *Creat(){ Node *head; IniNode(head); Node *p1,*p2; p1 = p2 = head; while(p1 -> next != NULL || p1 == head) { int a = 0; scanf("%d",&a); if(a < 0) { p1 -> next = NULL; break; } p1 = (Node *)malloc(sizeof(Node)); if(p1 == NULL) { printf("Overflow\n"); exit(1); } p1 -> data = a; p2 -> next = p1; p2 = p1; } return head;} 1. 在Creat里面，初始化Node的时候不能置NULL：
Node *head = NULL; // Error. IniNode(head);
2. 其次，在构建链表的时候，需要注意p2 始终跟在 p1的后面，起到link的作用。
p1 = (Node *)malloc(sizeof(Node)); ··· p1 -> data = a; p2 -> next = p1; // 这句话不要忘记 p2 = p1;
3. while循环条件，我的写法是刚刚开始时将p1 和p2 ，指向头节点。所以循环条件得:
while(p1 -> next != NULL || p1 == head)
否则，开始时
p1 -> next == NULL就没有办法进入循环进行输入。
- 输出部分:
void output(Node *head){ Node *p = head -> next; while(p != NULL) { printf("%d ",p -> data); p = p -> next; } printf("\n");} 注意：按照我的写法，开始赋值的时候，需要置p为
head -> next，否则无法进入循环。
- 插入部分：
void pinsert(Node *head){ Node *p1,*p2; p1 = p2 = head; int i_data = 0,num = 0; scanf("%d%d",&num,&i_data); int i,j; for(i = 1; i <= num; i++) { p2 = p1; p1 = p1 -> next; } Node *p; p = (Node *)malloc(sizeof(Node)); if(p == NULL) { printf("Overflow\n"); exit(1); } p -> next = p1; p -> data = i_data; p2 -> next = p; output(head);} 1. for循环条件需要根据p1 和 p2的初始指向确定。
p1 = p2 = head; ··· for(i = 1; i <= num; i++) // <= { p2 = p1; p1 = p1 -> next; } 否则会导致崩溃，指向错误。
2. 创立的新结点 同样需要
malloc语句
Node *p; p = (Node *)malloc(sizeof(Node)); if(p == NULL) { printf("Overflow\n"); exit(1); }
- 删除部分： (这里指的是删除结点)
void pdelete(Node *head){ Node *p1,*p2; p1 = p2 = head; int d_num = 0; scanf("%d",&d_num); int i,j; for(i = 1; i <= d_num; i++) { p2 = p1; p1 = p1 -> next; } p1 = p1 -> next; free(p2 -> next); // 勿忘我 p2 -> next = p1; output(head);} 注：和insert一样，需要根据p1 和p2 的初始指向确定循环范围。
- 最后需要释放内存
void pfree(Node *head){ Node *p1,*p2; p1 = p2 = head; while(p1 -> next != NULL) { p2 = p1; p1 = p1 -> next; free(p2); } if(p1 == head) free(p1);}