LeetCode024 Swap Nodes in Pairs

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详细见：leetcode.com/problems/swap-nodes-in-pairs/

Java Solution: github

package leetcode;import tools.ListNode辅助.ListNode;public class P024_SwapNodesInPairs {public static void main(String[] args) {ListNode input = tools.ListNode辅助.A_一维生成器(new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});tools.ListNode辅助.B_打印链表(new Solution2().swapPairs(input));}/* * 0 ms * 6.30% */static class Solution1 {    public ListNode swapPairs(ListNode head) {    if (head == null || head.next == null)    return head;        ListNode pre = head, cur = pre.next.next, tmp = null, ans = head.next;        pre.next.next = head;        head.next = cur;        boolean isOdd = true;        while (cur != null) {        if (! isOdd) {        tmp = cur.next;        cur.next = pre.next;        pre.next.next = tmp;        pre.next = cur;        pre = cur.next;        cur = pre.next;        } else {        cur = cur.next;        }        isOdd = ! isOdd;        }        return ans;    }}/* * 1的问题就是代码太麻烦 * 一定要有更加简洁的代码 * 0 ms * 6.30% */static class Solution2 {    public ListNode swapPairs(ListNode head) {    if (head == null || head.next == null)    return head;        ListNode pre = head, cur = pre.next.next, next_cur = null, ans = head.next;        pre.next.next = head;        head.next = cur;        boolean isOdd = true;        while (cur != null) {        if (! isOdd) {        next_cur = cur.next;        cur.next = pre.next;        pre.next = cur;        cur = cur.next;        cur.next = next_cur;        pre = cur;        cur = next_cur;        } else {        cur = cur.next;        }        isOdd = ! isOdd;        }        return ans;    }}}

C Solution: github

/*    url: leetcode.com/problems/swap-nodes-in-pairs/    6ms 0.0%*/#include <stdio.h>#include <stdlib.h>struct ListNode {    int val;    struct ListNode *next;};struct ListNode * convert_int_to_ListNode(int * arr, int n) {    struct ListNode * head = NULL;    struct ListNode * travel = NULL;    struct ListNode * temp = NULL;    int i = 0;    if (n == 0 || n < 0) return NULL;    travel = (struct ListNode *) malloc(sizeof(struct ListNode));    travel->val = *(arr + 0);    travel->next = NULL;    head = travel;    for (i = 1; i < n; i ++) {        temp = (struct ListNode *) malloc(sizeof(struct ListNode));        temp->val = *(arr + i);        temp->next = NULL;        travel->next = temp;        travel = travel->next;    }    return head;}void free_ListNode(struct ListNode * l) {    struct ListNode * temp = NULL;    while (l != NULL) {        temp = l->next;        free(l);        l = temp;    }}void print_ListNode(struct ListNode * h) {    while (h != NULL) {        printf("%d ", h->val);        h = h->next;    }    printf("\r\n");}struct ListNode* swapPairs(struct ListNode* head) {    struct ListNode * t1 = head, * t2 = NULL, * t3 = NULL, * t0 = NULL;    struct ListNode * answer = head;    t2 = t1 == NULL ? NULL : t1->next;    t3 = t2 == NULL ? NULL : t2->next;    while (t2 != NULL) {        t2->next = t1;        if (t0 != NULL)            t0->next = t2;        if (head == answer)            answer = t2;        t0 = t1;        t1 = t3;        t2 = t1 == NULL ? NULL : t1->next;        t3 = t2 == NULL ? NULL : t2->next;    }    if (t0 != NULL)        t0->next = t1;    return answer;}int main() {    int a[] = {1};    struct ListNode * l = convert_int_to_ListNode(a, 1);    struct ListNode * answer = swapPairs(l);    print_ListNode(answer);    free_ListNode(answer);}

Python Solution: github

#coding=utf-8'''    url: leetcode.com/problems/swap-nodes-in-pairs/    @author:     zxwtry    @email:      zxwtry@qq.com    @date:       2017年3月31日    @details:    Solution: 52ms 31.83%'''from leetcode.Utils import *class Solution(object):    def swapPairs(self, head):        if head == None: return head        ans = head.next if head.next != None else head        t0, t1, t2, t3 = None, head, head.next, None if \        head.next == None else head.next.next        while t2 != None:            t2.next = t1            t1.next = t3            if t0 != None:                t0.next = t2            t0, t1, t2 = t1, t3, None if t3 == None else t3.next            t3 = None if t2 == None else t2.next        return ansif __name__ == "__main__":    head = convertArrayToListNode([1, 2, 3, 4, 5, 6, 7, 8])    sol = Solution()    printListNode(sol.swapPairs(head))

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