Datawhale编程实践（LeetCode 腾讯精选练习50）Task5

1.合并K个升序链表https://leetcode-cn.com/problems/merge-k-sorted-lists/

这题是leetcode的一个困难题

这里对将两个升序链表进行合并进行了复习，C++代码如下

ListNode* mergeTwoLists(ListNode *a, ListNode *b) {
    if ((!a) || (!b)) return a ? a : b;
    ListNode head, *tail = &head, *aPtr = a, *bPtr = b;
    while (aPtr && bPtr) {
        if (aPtr->val < bPtr->val) {
            tail->next = aPtr; aPtr = aPtr->next;
        } else {
            tail->next = bPtr; bPtr = bPtr->next;
        }
        tail = tail->next;
    }
    tail->next = (aPtr ? aPtr : bPtr);
    return head.next;
}

还学到了优先队列的思想，利用python的heapq模块，通过堆进行优先队列的实现

class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:
    def mergeKLists(self, lists: List[ListNode]) -> ListNode:
        if not lists or len(lists) == 0:
            return None
        import heapq
        heap = []
        # 首先 for 嵌套 while 就是将所有元素都取出放入堆中
        for node in lists:
            while node:
                heapq.heappush(heap, node.val)
                node = node.next
        dummy = ListNode(None)
        cur = dummy
        # 依次将堆中的元素取出(因为是小顶堆，所以每次出来的都是目前堆中值最小的元素），然后重新构建一个列表返回
        while heap:
            temp_node = ListNode(heappop(heap))
            cur.next = temp_node
            cur = temp_node
        return dummy.next

2.删除排序数组中的重复项https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/

3.搜索旋转排序数组https://leetcode-cn.com/problems/search-in-rotated-sorted-array/