两种删除单链表结点的实现，一种O(n),一种O(1)

常规的删除单链表结点的做法是挨个查找到该结点的前一个结点，然后去掉要删除的这个结点，回收内存。这个需要O(n)的时间。

有一种比较快速的删除掉链表指定一个节点的方法，就是把下一个结点的内容复制到当前这个结点，然后把下一次结点删除掉，这个需要考虑当要删除的结点是最后一个结点的情况。

如果刚好是最后一个结点，则需要O(n)的时间，如果不是最后一个结点，可以在O(1)时间内完成删除操作。

//
//  main.c
//  SingleListDeleteNode
//
//  Created by xxx on 6/20/14.
//  Copyright (c) 2014 xxx. All rights reserved.
//

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    struct Node *next;
    int value;
}Node;

Node* genList(int *content, int length);
void printList(Node *header);
void releaseList(Node *header);
void normalDeleteNode(Node *header, Node *node);
void fashDeleteNode(Node *header, Node *node);
Node* getNodeAtIndex(Node *header, int index);

int main(int argc, const char * argv[])
{

    // insert code here...
    printf("Hello, World!
");
    
    Node *header = NULL;
    int values[10] = {1,2,3,4,5,6,7,8,9,0};
    header = genList(values, 10);
    printList(header);
    releaseList(header);
    

    printf("show normal delete node result!
");
    header = genList(values, 10);
    Node *nodeToDel = getNodeAtIndex(header, 3);
    normalDeleteNode(header, nodeToDel);
    printList(header);
    releaseList(header);

    printf("show fast delete node result!
");
    header = genList(values, 10);
    nodeToDel = getNodeAtIndex(header, 3);
    fashDeleteNode(header, nodeToDel);
    printList(header);
    releaseList(header);
    
    
    
    return 0;
}

Node* genList(int *content, int length) {
    Node *header = NULL;
    Node *curNode = NULL;
    for (int i=0; i<length; i++) {
        Node *tmp = (Node *)malloc(sizeof(Node));
        tmp->value = content[i];
        if (i == 0) {
            header = tmp;
        }
        if (curNode != NULL) {
            curNode->next = tmp;
        }
        curNode = tmp;
    }
    curNode->next = NULL;
    return header;
}

void releaseList(Node *header) {
    while (header != NULL) {
        Node *tmp = header;
        header = header->next;
        tmp->next = NULL;
        free(tmp);
        tmp = NULL;
    }
}

void printList(Node *header) {
    printf("LIST : ");
    while (header != NULL) {
        printf("%d",header->value);
        if (header->next != NULL) {
            printf(" -> ");
        }
        header = header->next;
    }
    printf("
");
}

void normalDeleteNode(Node *header, Node *node) {
    while (header->next != node) {
        header = header->next;
        if (header == NULL) {
            return;
        }
    }
    header->next = header->next->next;
    free(node);
    node = NULL;
}

void fashDeleteNode(Node *header, Node *node) {
    if (node->next == NULL) {
        while (header->next != node) {
            header = header->next;
        }
        header->next = NULL;
        free(node);
        node = NULL;
        return;
    }
    node->value = node->next->value;
    Node *tmp = node->next;
    node->next = node->next->next;
    free(tmp);
    tmp = NULL;
}

Node* getNodeAtIndex(Node *header, int index) {
    while (index > 0 && header != NULL) {
        header = header->next;
        index--;
    }
    return header;
}