c - 合并两个链表
问题描述
我有一个任务,我必须在不创建新列表的情况下按升序将两个链表组合在一个函数中。像这样的东西:[1.3-->3.2-->4.6-->7.0]
& [2.7-->2.9-->5.1]
-> [1.3-->2.7-->2.9-->3.2-->4.6-->5.1-->7.0]
。我有整个代码,但监控程序一直报告相同:MEMORY LEAK
.
这是我的代码(只有功能部分和struct
定义):
typedef struct _listelem {
double data;
struct _listelem *next;
} listelem;
listelem *merge(listelem *a, listelem *b) {
listelem *lemarado = NULL;
listelem *mozgo = a;
listelem *elol2 = b;
lemarado = mozgo;
if (elol2 == NULL) // if the list is zero
return a;
else
if (mozgo == NULL)
return b;
if (mozgo->next == NULL) { //if the first list has only one element
while (elol2 != NULL) {
listelem *vege;
vege = (listelem *)malloc(sizeof(listelem));
vege->data = elol2->data;
lemarado->next = vege;
free(vege);
lemarado = lemarado->next;
elol2 = elol2->next;
}
lemarado->next = NULL;
return a;
}
mozgo = mozgo->next; // I am maintaining a pointer which points to the next data, and a pointer
while (mozgo != NULL) { // Which points to the data before, and I stick an element between them
if (elol2 == NULL) {
while (mozgo != NULL)
mozgo = mozgo->next;
while (lemarado != NULL)
lemarado = lemarado->next;
return a;
}
if (mozgo->data > elol2->data) {
listelem *hozzafuz;
hozzafuz = (listelem *)malloc(sizeof(listelem));
hozzafuz->data = elol2->data;
lemarado->next = hozzafuz;
hozzafuz->next = mozgo;
elol2 = elol2->next;
lemarado = lemarado->next;
} else {
mozgo = mozgo->next;
lemarado = lemarado->next;
}
if (mozgo == NULL) {
while (elol2 != NULL) {
listelem *vege;
vege = (listelem *)malloc(sizeof(listelem));
vege->data = elol2->data;
lemarado->next = vege;
free(vege);
lemarado = lemarado->next;
elol2 = elol2->next;
}
lemarado->next = NULL;
}
}
return a;
}
解决方案
无需分配空闲列表节点,您只需将已排序的列表合并为一个列表即可。对于不会说匈牙利语的人来说,使用非英语变量名会让人感到困惑,恐怕这很常见。
这是修改后的版本:
typedef struct _listelem {
double data;
struct _listelem *next;
} listelem;
listelem *merge(listelem *a, listelem *b) {
listelem *head = NULL;
listelem *tail = NULL;
if (b == NULL)
return a;
else
if (a == NULL)
return b;
if (a->data <= b->data) {
head = a;
a = a->next;
} else {
head = b;
b = b->next;
}
tail = head;
while (a != NULL && b != NULL) {
if (a->data <= b->data) {
tail->next = a;
a = a->next;
} else {
tail->next = b;
b = b->next;
}
tail = tail->next;
}
if (a == NULL)
tail->next = b;
else
tail->next = a;
return head;
}
如果你掌握了双指针,上面的代码可以简化为:
listelem *merge(listelem *a, listelem *b) {
listelem *head = NULL;
for (listelem **link = &head;; link = &(*link)->next) {
if (a == NULL) {
*link = b;
break;
}
if (b == NULL) {
*link = a;
break;
}
if (a->data <= b->data) {
*link = a;
a = a->next;
} else {
*link = b;
b = b->next;
}
}
return head;
}
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