提示:设置一前一后两个指针,一个指针步长为1,另一个指针步长为n,当一个指针走到链表尾端时,
另一指针指向的元素即为链表倒数第n个元素。
#include <stdio.h>
#include <stdlib.h>
#include "LinkList.h"
void createLinkList(LNode **p) {
setnull(p); /*建议链表并设置为空表*/
int n = 10, i;
srand(time(0));
for (i = 1; i <= n; i++) {
insert(p, rand() % 100 + 1, i);
} /*插入数据到链表*/
}
LNode* getLNodeByIndex(LNode* head, int index) {
if (!head || index < 1) {
return NULL;
}
int j = 1;
LNode *q = head;
while (j < index && q != null) {
q = q->next;
j++;
}
if (q != null) {
return q;
} else {
printf("位置参数不正确!\n");
return NULL;
}
}
LNode* getNumByIndexFromRear(LNode* head, int index) {
LNode* begin = head;
LNode* end = getLNodeByIndex(head, index);
if (!end) {
return NULL;
}
while (end->next) {
begin = begin->next;
end = end->next;
}
return begin;
}
LNode* findLastElem(LNode* head, int last) {
if (!head) {
return NULL;
}
LNode* prev = head;
LNode* next = head;
while (last-- && next) {
next = next->next;
}
if (last+1) {
return NULL;
}
while (next) {
prev = prev->next;
next = next->next;
}
return prev;
}
int main(void) {
setvbuf(stdout, NULL, _IONBF, 0);
LNode *head; /*定义静态变量*/
createLinkList(&head);
display(&head); /*显示链表所有数据*/
int index = 3;
puts("input last index:");
scanf("%d", &index);
// LNode* node = getNumByIndexFromRear(head, index);
LNode *node = findLastElem(head, index);
if (node) {
printf("LastIndex%3d:, Elem:%3d\n", index, node->data);
} else {
puts("Invalid Input.");
}
return EXIT_SUCCESS;
}