23.02.03 Today’s Leetcode

6. Zigzag Conversion (medium)

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        if numRows == 1:
            return s
        temp = [[] for x in range(numRows)]
        cur, dir = 0, 0
        for c in s:
            temp[cur].append(c)
            if cur == 0:
                dir = 1
            elif cur == numRows - 1:
                dir = -1
            cur = cur + dir
        res = ''
        for p in temp:
            res += ''.join(p)
        return res

147. Insertion Sort List (medium)

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def insertionSortList(self, head):

        dummyHead = ListNode(0)
        dummyHead.next = nodeToInsert = head
        
        while head and head.next:
            if head.val > head.next.val:
                # Locate nodeToInsert.
                nodeToInsert = head.next
                # Locate nodeToInsertPre.
                nodeToInsertPre = dummyHead
                while nodeToInsertPre.next.val < nodeToInsert.val:
                    nodeToInsertPre = nodeToInsertPre.next
                    
                head.next = nodeToInsert.next
                # Insert nodeToInsert between nodeToInsertPre and nodeToInsertPre.next.
                nodeToInsert.next = nodeToInsertPre.next
                nodeToInsertPre.next = nodeToInsert
            else:
                head = head.next
            
        return dummyHead.next