leetcode2.18-2.19两次周赛做出了7t（有一t赶着去吃饭没做了可惜）

src

class Solution:
    def countEven(self, num: int) -> int:
        def cnt(x):
            sum1 = 0
            while x != 0:
                sum1 += x % 10
                x //= 10
            return sum1
        
        ans = 0
        for i in range(1, num + 1):
            if cnt(i) % 2 == 0:
                ans += 1
        
        return ans

src

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def mergeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
        value = []
        p = head
        tempsum = 0
        while p != None:
            tempsum += p.val
            if p.val == 0:
                if tempsum > 0:
                    value.append(tempsum)
                tempsum = 0
            
            p = p.next
        print(value)
        p = head
        n = len(value)
        for i in range(n):
            if i == 0:
                p.val = value[i]
            else:
                q = ListNode(value[i])
                p.next = q
                p = q
        if n == 1:
            p.next = None
        return head

思路：
用dict反向模拟，比较恶心，要根据答案改bug
用pre记录前一个

class Solution:
    def repeatLimitedString(self, s: str, repeatLimit: int) -> str:
        cnt = defaultdict(int)
        for c in s:
            cnt[ord(c) - ord('a')] += 1
        #print(cnt)
        cnt = sorted(cnt.items(), key = lambda x: -x[0])
        
        
        cnt = [list(i) for i in cnt]
        #print(cnt)
        ans = ""
        now = 0
        pre = -1
        while now < len(cnt):
            if pre != -1 and cnt[pre][1] > 0 and now != pre:
                if cnt[now][1] > 0:
                    ans += chr(ord('a') + cnt[now][0])
                
                    cnt[now][1] -= 1
                    now = pre
                    continue
                    #print(ans)
                    #print(cnt)
                else:
                    now += 1
                    continue
                    
            
            if cnt[now][1] <= repeatLimit:
                ans += chr(ord('a') + cnt[now][0]) * cnt[now][1]   
                cnt[now][1] = 0
                now += 1
                #print(ans)
                #print(cnt)
            else:
                ans += chr(ord('a') + cnt[now][0]) * repeatLimit
                cnt[now][1] -= repeatLimit
                pre = now
                now += 1
                #print(ans)
                #print(cnt)
        
        return ans

思路：
找出gcd，然后判断它们乘积就好

src：

class Solution:
    def coutPairs(self, nums: List[int], k: int) -> int:
        def gcd(x, y):
            if y != 0:
                return gcd(y, x % y)
            return x
        
        gcdDict = defaultdict(int)
        for num in nums:
            gcdDict[gcd(num, k)] += 1
        
        ans = 0
        #print(gcdDict)
        
        keys = list(gcdDict.keys())
        #print(keys)
        n = len(keys)
        
        for i in range(n):
            for j in range(i, n):
                if i != j and (keys[i] * keys[j]) % k == 0:
                    ans += gcdDict[keys[i]] * gcdDict[keys[j]]
                elif i == j and (keys[i] * keys[j]) % k == 0:
                    ans += gcdDict[keys[i]] * (gcdDict[keys[i]] - 1) // 2
        
        return ans

src：

class Solution:
    def countPairs(self, nums: List[int], k: int) -> int:
        n = len(nums)
        ans = 0
        for i in range(n):
            for j in range(i + 1, n):
                if nums[i] == nums[j] and (i * j) % k == 0:
                    ans += 1
        return ans

src：

class Solution:
    def sumOfThree(self, num: int) -> List[int]:
        ans = []
        if num % 3 == 0:
            mid = num // 3
            ans.append(mid - 1)
            ans.append(mid)
            ans.append(mid + 1)
        return ans

思路：
处以2后，按12345这样求和得到1，3，6，10看看总和夹在哪个位置
然后填数字的时候就从12345填入，最后补充剩余的一个即可

src：

class Solution:
    def maximumEvenSplit(self, finalSum: int) -> List[int]:
        if finalSum % 2 == 1:
            return []
        
        sum1 = finalSum // 2
        ans = 0
        k = 0
        flag = False
        left = 0
        right = 0xffffffff
        while left < right:
            mid = (left + right) // 2 + 1
            cnt = mid * (mid + 1) // 2
            if cnt == sum1:
                k = mid
                flag = True
                break
            elif cnt > sum1:
                right = mid - 1
            else:
                left = mid
        
        if flag:
            ans = k
        else:
            ans = left
        
        res = []
        temp = 0
        for i in range(1, ans):
            res.append(2 * i)
            temp += 2 * i
        res.append(finalSum - temp)
        return res

总结：
有进步！第二次周赛没写完最后一个hard着实有点可惜！