Leetcode 92:反转链表 II

Seawolf

Code:

#include <stdio.h>

struct Node{

    int val;

    struct Node *next;

};


struct Node * reverseList1(struct Node *hd, int n, int m){

    int change_len = m - n + 1;

    struct Node * result = hd;

    struct Node * pre_head = NULL;

    while(hd && --n){

        pre_head = hd;

        hd = hd->next;

    }

    struct Node * modify_node_tail = hd;

    struct Node * newHead = NULL;

    while(hd && change_len){

        struct Node *next = hd->next;

        hd->next = newHead;

        newHead = hd;

        hd = next;

        change_len = change_len -1;

    }

    modify_node_tail->next = hd;

    if(pre_head){

        pre_head -> next = newHead;
    }
    else{

        result = newHead;
    }


    return result;
}

int main(void){

    struct Node a;
    struct Node b;
    struct Node c;
    struct Node d;
    struct Node e;

    a.val = 10;
    b.val = 20;
    c.val = 30;
    d.val = 40;
    e.val = 50;

    a.next = &b;
    b.next = &c;
    c.next = &d;
    d.next = &e;
    e.next = NULL;

    struct Node * head = &a;

    while(head){

        printf("%d\n", head->val);

        head = head->next;

    }

    printf("----------\n");

    struct Node * head_2 = &a;

    int x = 2;

    int y = 4;

    struct Node *ptr_1 = reverseList1(head_2, x, y);

    while(ptr_1){

        printf("%d\n", ptr_1->val);

        ptr_1 = ptr_1->next;

    }

    printf("----------\n");

    return 0;
}

Output:

10
20
30
40
50
----------
10
40
30
20
50
----------