365天挑战LeetCode1000题——Day 264 周赛336

第一题：遍历

class Solution {
public:
    int vowelStrings(vector<string>& words, int left, int right) {
        unordered_set<char> st = {'a', 'e', 'i', 'o','u'};
        int cnt = 0;
        for (int i = left; i <= right; i++) {
            if (st.count(words[i][0]) && st.count(words[i].back())) cnt++;
        }
        return cnt;
    }
};

第二题：贪心

class Solution {
public:
    int maxScore(vector<int>& nums) {
        sort(nums.begin(), nums.end(), [](int a, int b) {
            return a > b;
        });
        long long cnt = 0;
        int score = 0;
        for (int x : nums) {
            cnt += x;
            if (cnt > 0) score++;
        }
        return score;
    }
};

第三题：前缀和 + 哈希表

class Solution {
public:
    long long beautifulSubarrays(vector<int>& nums) {
        long long ans = 0;
        unordered_map<int, int> mp;
        int cur = 0;
        mp[0] = 1;
        for (int x : nums) {
            cur ^= x;
            if (mp.count(cur)) ans += mp[cur];
            mp[cur]++;
        }
        return ans;
    }
};

第四题：贪心 + 暴力

class Solution {
public:
    int findMinimumTime(vector<vector<int>>& tasks) {
        int cnt = 0;
        vector<bool> run(2001, false);
        sort(tasks.begin(), tasks.end(), [](vector<int> a, vector<int> b) {
            return a[1] < b[1];
        });
        int s, e, d;
        for (auto task : tasks) {
            s = task[0], e = task[1], d = task[2];
            d -= accumulate(run.begin() + s, run.begin() + e + 1, 0);
            if (d > 0) {
                for (int i = e; i >= d; i--) {
                    if (!run[i]) {
                        run[i] = true;
                        cnt++;
                        d--;
                        if (d == 0) break;
                    }
                }
            }
        }
        return cnt;
    }
};