[英]C Linked List Bubble Sort Logic Error
下面我有一个简单的 C 语言链表程序,它保存一个点及其与原点的距离。 我的问题是,调用排序函数时,排序不正确。 我花了很多时间用 gdb 调试,但没有运气。 我对 C 和处理指针比较陌生,所以如果有人能帮助我,我将不胜感激!
我打算发布输出的图像,但我似乎没有足够的声誉,所以输出看起来如下所示:
点:(3,1) - 距离:3.16228
点:(4,1) - 距离:4.12311
点:(1,1) - 距离:1.41421
点:(7,1) - 距离:7.07107
test.c 文件:
#include <stdlib.h>
#include <stdio.h>
#include "point.h"
typedef struct node
{
Point p;
double distance;
struct node *next;
} node;
void insertAtFront(node **start, Point *ip);
void sort(node *start);
void swap(node *a, node *b);
void printList(node *start);
int main(int argc, char **argv)
{
Point *insertPoint = malloc(sizeof(Point));
node *head = NULL;
point_set(insertPoint,7.0,1.0);
insertAtFront(&head,insertPoint);
point_set(insertPoint,1.0,1.0);
insertAtFront(&head,insertPoint);
point_set(insertPoint,4.0,1.0);
insertAtFront(&head,insertPoint);
point_set(insertPoint,3.0,1.0);
insertAtFront(&head,insertPoint);
sort(head);
printList(head);
}
void insertAtFront(node **start, Point *ip)
{
node *node1 = (node*)malloc(sizeof(node));
node1->p = *ip;
node1->next = *start;
*start = node1;
}
void sort(node *start)
{
Point *tp1 = malloc(sizeof(Point));
Point *tp2 = malloc(sizeof(Point));
int swapped;
node *node1;
node *node2 = NULL;
node *tempNode;
double d1;
double d2;
if(start == NULL)
return;
do
{
swapped = 0;
node1 = start;
*tp1 = node1->p;
tempNode = node1->next;
*tp2 = tempNode->p;
d1 = distanceFromOrigin(tp1);
d2 = distanceFromOrigin(tp2);
while(node1->next != node2)
{
if(d1 > d2)
{
swap(node1,node1->next);
swapped = 1;
}
node1 = node1->next;
}
node2 = node1;
}
while(swapped);
}
void swap(node *a, node *b)
{
Point *tp;
*tp = a->p;
a->p = b->p;
b->p = *tp;
}
void printList(node *start)
{
node *temp = start;
Point *tp = malloc(sizeof(Point));
printf("\n");
while(temp != NULL)
{
*tp = temp->p;
printf("Point: (%g,%g) - Distance: %g\n", point_getX(tp), point_getY(tp), distanceFromOrigin(tp));
temp = temp->next;
}
}
point.c 文件:
#include <stdio.h>
#include "point.h"
#include <math.h>
void point_translate(Point *p, double x, double y)
{
point_set(p,(point_getX(p)+x),(point_getY(p)+y));
}
double point_distance(const Point *p1, const Point *p2)
{
double temp1 = (point_getX(p1) - point_getX(p2));
double temp2 = (point_getY(p1) - point_getY(p2));
double temp3 = (temp1*temp1)+(temp2*temp2);
double dist = sqrt(temp3);
return dist;
}
double distanceFromOrigin(const Point *p1)
{
double x = point_getX(p1);
double y = point_getY(p1);
double temp = (x*x)+(y*y);
double dist = sqrt(temp);
return dist;
}
点.h文件:
#ifndef _POINT_H_
#define _POINT_H_
typedef struct Point
{
double x;
double y;
} Point;
void point_translate(Point *p, double x, double y);
double point_distance(const Point *p1, const Point *p2);
double distanceFromOrigin(const Point *p1);
static inline double point_getX(const Point *p)
{
return p->x;
}
static inline double point_getY(const Point *p)
{
return p->y;
}
static inline Point *point_set(Point *p, double x, double y)
{
p->x = x;
p->y = y;
return p;
}
#endif
“交换”函数中的局部变量 tp 未初始化。 你的编译器应该警告你这一点。 然后你无论如何都可以访问它,这是未定义的行为......
当node1和node1->next交换node1时,需要改变前一个节点指向node1的next指针,也可以交换node1和node1->next之间的数据,保持next指针不变。
如果您要交换指针,这是交换前的样子:
node0->next = node1, node1->next = node2, node2->next = node3
和交换后:
node0->next = node2, node2->next = node1, node1->next = node3
这仅适用于相邻节点。 如果节点不相邻,则在交换之前:
nodea->next = node1, node1->next = nodeb
nodec->next = node2, node2->next = noded
交换后
nodea->next = node2, node2->next = nodeb
nodec->next = node1, node1->next = noded
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.