6889. 特殊元素平方和 - 力扣（LeetCode）

思路：模拟

class Solution {
public:int sumOfSquares(vector<int>& nums) {int res = 0;for(int i = 0; i < nums.size(); i ++ ){if(nums.size() % (i + 1) == 0) res += nums[i] * nums[i];}return res;}
};

6929. 数组的最大美丽值 - 力扣（LeetCode）

思路：排序+双指针

class Solution {
public:int maximumBeauty(vector<int>& nums, int k) {int n = nums.size();int res = 0, left = 0;sort(nums.begin(), nums.end());for(int right = 0; right < n; right ++ ){while (nums[right] - nums[left] > k * 2) left ++ ;res = max(res, right - left + 1);}return res;}
};

6927. 合法分割的最小下标 - 力扣（LeetCode）

思路：哈希+枚举

class Solution {
public:int minimumIndex(vector<int>& nums) {map<int, int> mp;int k = 0, cnt = 0;for(int t : nums){mp[t] ++ ;if(mp[t] > cnt){cnt = mp[t];k = t;}}int n = nums.size();int count = 0;for(int i = 0; i < n; i ++ ){if(nums[i] == k) count ++ ;if(count > (i + 1) / 2 && (cnt - count) > (n - 1 - i) / 2) return i;}return -1;}
};

6924. 最长合法子字符串的长度 - 力扣（LeetCode）

思路：哈希+双指针

class Solution {
public:int longestValidSubstring(string word, vector<string>& forbidden) {unordered_set<string> se{forbidden.begin(), forbidden.end()};int res = 0, left = 0, n = word.size();for(int right = 0; right < n; right ++ ){for(int i = right; i >= left && i > right - 10; i -- ){if(se.count(word.substr(i, right - i + 1))){left = i + 1;break;}}res = max(res, right - left + 1);}return res;}
};