Weekly Contest 315

Problem A

Largest Positive Integer That Exists With Its Negative

思路

按照题目要求暴力求一下

代码

class Solution:
    def findMaxK(self, nums: List[int]) -> int:
        ans = -1
        for item in nums:
            if (-item) in nums:
                ans = max(ans,abs(item))
        return ans

Problem B

Count Number of Distinct Integers After Reverse Operations

思路

题目的本意就是将数组中每一个元素反转然后加入到数组中，求一下数组中不重复的个数，用set就行

代码

class Solution:
    def countDistinctIntegers(self, nums: List[int]) -> int:
        s = set()
        for item in nums:
            r = int(str(item)[::-1])
            s.add(r)
            s.add(item)
        return len(s)

Problem C

Sum of Number and Its Reverse

思路

暴力遍历从小到大, 复杂度为$O(n^2)$ 不知道为啥能过

代码

class Solution:
    def sumOfNumberAndReverse(self, num: int) -> bool:
        if num == 0:
            return True
        for i in range(1,num):
            if i == int(str(num-i)[::-1]):
                return True
        return False

Problem D

Count Subarrays With Fixed Bounds

思路

优先使用不在区间内的值将原数组划分成几部分，随后在每个部分中，先确定一个包含最大最小值的最小区间，然后按照一个方向延伸即可，具体实现用的双指针

代码

class Solution {
public:
    long long countSubarrays(vector<int>& nums, int minK, int maxK) {
        long long ret = 0;
        int smin = 0, smax = 0;
        for (int i = 0, j = 0, last = 0; i < nums.size(); i++) {
            if (nums[i] < minK || nums[i] > maxK) {
                last = j = i + 1;
                smin = smax = 0;
            }
            else {
                if (nums[i] == minK) smin++;
                if (nums[i] == maxK) smax++;
                while (j < i) {
                    if (nums[j] == minK) smin--;
                    if (nums[j] == maxK) smax--;
                    if (!smin || !smax) {
                        if (nums[j] == minK) smin++;
                        if (nums[j] == maxK) smax++;
                        break;
                    }
                    j++;
                }
                if (smin && smax) ret += j - last + 1;
            }
        }
        return ret;
    }
};
 

总结

出了3题，但是感觉状态越来越不好了，水平下滑有点严重。