[leetcode] 시험

1. 투썸플레이스

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        if len(nums) == 2:
            return [0,1]
        
        for i in range(0, len(nums)):
            for j in range(i+1, len(nums)):
                if nums[i]+nums[j] == target:
                    return [i,j]

아 거저주려고 냈구나 했는데..^^
생각보다 생각을 해야해서 당황했던 문제..
이중 for 문이와 재결합했어요^^

121. Best Time to Buy and Sell Stock

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        if len(prices) < 1:
            return 0
        
        buy = prices[0]
        sell = 0
        profit = 0
        
        for i in range(1, len(prices)):
            if buy > prices[i]:
                buy = prices[i]
            else:
                sell = prices[i]
                profit = max(profit, sell-buy)
                
        return profit

내 트라우마였던 stock...
이건 확실하게 이해하고 풀었읍니다.

70. Climbing Stairs

class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        
        first = 1
        second = 2
        
        for i in range(3, n+1):
            third = first + second
            first = second
            second = third
            
        return second

내 트라우마 2번째...
이것도 피보나치였다는걸 깨닫고 풀었읍니다.

202. unHappy number

class Solution:
    def isHappy(self, n: int) -> bool:
        #지금이상황..데자뷰같다
        if n == 1:
            return True
        
        result = 0
        tmp = 0
        
        while n:
            result += pow(n%10, 2)
            n //= 10
        
        if result == 4:
            return False
        else:
            return self.isHappy(result)

갑자기 오류나서 당황했는데 똘추짓한거였음
이거도 ㄱㅊ~

160. Intersection of Two Linked Lists 극혐

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

class Solution:
    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode:
        #my trauma
        #asjflasmdlfmalw내머리는너무나나빠서
        
        hA = headA
        hB = headB
        
        while hA != hB:
            hA = headB if not hA else hA.next
            hB = headA if not hB else hB.next
        
        return hA

솔직히 이건.. 기억에 의존했읍니다

234. Palindrome Linked List

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def isPalindrome(self, head: ListNode) -> bool:
        if head is None or head.next is None:
            return True
        
        head2 = head
        listA = []
        while head2:
            listA.append(head2.val)
            head2 = head2.next
        
        while head:
            if listA.pop() != head.val:
                return False
            head = head.next
            
        return True

이거도 트라우마때 강렬했는지 잘 생각이 나더군요