some more solves

contests/5contest/3.cpp

@@ -12,17 +12,17 @@ struct Date {
     int M;
     int D;
 
-    Date(std::string s) {
+    Date(std::string& s) {
         std::stringstream ss;
         ss << s;
-        
+
         char tmp;
         ss >> Y >> tmp >> M >> tmp >> D;
     }
 
     Date(int Y, int M, int D) : Y(Y), M(M), D(D) {}
 
-    bool operator<(const Date d) const {
+    bool operator<(const Date& d) const {
         if (Y < d.Y) return true;
         if (Y > d.Y) return false;
 
@@ -30,7 +30,7 @@ struct Date {
         if (M > d.M) return false;
 
         if (D < d.D) return true;
-        
+
         return false;
     }
 
@@ -40,18 +40,18 @@ struct Student {
     std::map<Date, int> scores;
     std::string name;
 
-    Student(std::string name) : name(name) {}
+    Student(std::string& name) : name(name) {}
 
     Student(const Student& s) {
         scores = s.scores;
         name = s.name;
     }
 
-    bool operator==(const std::string n) {
+    bool operator==(const std::string& n) {
         return n == name;
     }
 
-    bool operator<(const Student st) const {
+    bool operator<(const Student& st) const {
         return name < st.name;
     }
 };
@@ -65,7 +65,7 @@ int main() {
     while (std::cin >> name >> date >> grade) {
         std::set<Student>::iterator iter = studs.find(name);
         Date d(date);
-        
+
         if (iter == studs.end()) {
             Student s(name);
             s.scores[d] = grade;
@@ -80,25 +80,19 @@ int main() {
         dates.insert(d);
     }
 
-    // std::cout << studs.size() << std::endl;
-    // std::cout << studs[0].name << studs[0].scores.size() << std::endl;
-
-    // std::sort(dates.begin(), dates.end());
-    // std::sort(studs.begin(), studs.end());
-
     std::cout << '.' << "\t";
     for (auto& date : dates) {
         std::cout << std::setfill('0')
-              << std::setw(4) << date.Y << '/'
-              << std::setw(2) << date.M << '/'
-              << std::setw(2) << date.D << '\t';
+            << std::setw(4) << date.Y << '/'
+            << std::setw(2) << date.M << '/'
+            << std::setw(2) << date.D << '\t';
     }
     std::cout << std::endl;
 
     for (auto st : studs) {
         std::cout << st.name << '\t';
 
-        for (auto date : dates) {
+        for (auto& date : dates) {
             if (st.scores.find(date) == st.scores.end()) {
                 std::cout << '.' << '\t';
             } else {