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奖励最顶尖的 k 名学生(哈希表+排序)

用哈希表对所有的positive与negative词条进行映射，然后遍历求解。tip：常用的分割字符串的操作：1.stringstream配合getline() [格式buf, string, char]2.string.find()[find未找到目标会返回npos]配合string.substr()

class Solution {
public:vector<int> topStudents(vector<string>& positive_feedback, vector<string>& negative_feedback, vector<string>& report, vector<int>& student_id, int k) {unordered_set<string> pos, neg;for (auto& s : positive_feedback) pos.insert(s);for (auto& s : negative_feedback) neg.insert(s);vector<pair<int, int>> arr;int n = student_id.size();for (int i = 0; i < n; ++i) {stringstream ss;ss << report[i];string tmp;int res = 0;while (getline(ss, tmp, ' ')) {if (pos.count(tmp)) res += 3; else if (neg.count(tmp)) res--;}arr.push_back({-res, student_id[i]});}sort(arr.begin(), arr.end());vector<int> ans(k);for (int i = 0; i < k; ++i) ans[i] = arr[i].second;return ans;}
};