PAT1039: Course List for Student

1039. Course List for Student (25)

时间限制

200 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

Zhejiang University has 40000 students and provides 2500 courses. Now given the student name lists of all the courses, you are supposed to output the registered course list for each student who comes for a query.

Input Specification:

Each input file contains one test case. For each case, the first line contains 2 positive integers: N (<=40000), the number of students who look for their course lists, and K (<=2500), the total number of courses. Then the student name lists are given for the courses (numbered from 1 to K) in the following format: for each course i, first the course index i and the number of registered students N_i (<= 200) are given in a line. Then in the next line, N_i student names are given. A student name consists of 3 capital English letters plus a one-digit number. Finally the last line contains the N names of students who come for a query. All the names and numbers in a line are separated by a space.

Output Specification:

For each test case, print your results in N lines. Each line corresponds to one student, in the following format: first print the student's name, then the total number of registered courses of that student, and finally the indices of the courses in increasing order. The query results must be printed in the same order as input. All the data in a line must be separated by a space, with no extra space at the end of the line.

Sample Input:

11 5
4 7
BOB5 DON2 FRA8 JAY9 KAT3 LOR6 ZOE1
1 4
ANN0 BOB5 JAY9 LOR6
2 7
ANN0 BOB5 FRA8 JAY9 JOE4 KAT3 LOR6
3 1
BOB5
5 9
AMY7 ANN0 BOB5 DON2 FRA8 JAY9 KAT3 LOR6 ZOE1
ZOE1 ANN0 BOB5 JOE4 JAY9 FRA8 DON2 AMY7 KAT3 LOR6 NON9

Sample Output:

ZOE1 2 4 5
ANN0 3 1 2 5
BOB5 5 1 2 3 4 5
JOE4 1 2
JAY9 4 1 2 4 5
FRA8 3 2 4 5
DON2 2 4 5
AMY7 1 5
KAT3 3 2 4 5
LOR6 4 1 2 4 5
NON9 0

思路

1.题目比较简单，关键是优化问题，如果直接用map<string,vector<int>>最后一个用例会超时，因为本身对map和string的操作相比char + 整数来说更耗时间。
2.所以得自己写一个简单的散列函数将名字散列为vector的整数索引来代替map，另外使用char数组存储名字而不是string，输入输出最好也换成scanf和printf而不是cin、cout。

超时代码

#include<iostream>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;

int main()
{
    int N,K;
    while(cin >> N >> K)
    {
        map<string,vector<int>> students;
        students.clear();
        for(int i = 0;i < K;i++)
        {
            int course,num;
            cin >> course >> num;
            for(int j = 0;j < num;j++)
            {
                string name;
                cin >> name;
                students[name].push_back(course);
            }
        }
        for(int i = 0;i < N;i++)
        {
            string name;
            cin >> name;
            cout << name << " " << students[name].size();
            sort(students[name].begin(),students[name].end());
            for(int j = 0;j < students[name].size();j++)
            {
                cout << " " << students[name][j];
            }
            cout << endl;
        }
    }
}

AC代码

#include<iostream>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;
const int maxnum = 26 * 26 * 26 * 10 + 1;

int HashName(char* name)
{
    return (name[0] - 'A') * 26 * 26 * 10 +
           (name[1] - 'A') * 26 * 10 +
           (name[2] - 'A') * 10 +
           (name[3] - '0');
}

int main()
{
    int N,K;
    while(cin >> N >> K)
    {
        vector<vector<int>> students(maxnum);
        char name[5];
        for(int i = 0;i < K;i++)
        {
            int course,num;
            cin >> course >> num;
            for(int j = 0;j < num;j++)
            {
                scanf("%s",name);
                students[HashName(name)].push_back(course);
            }
        }
        for(int i = 0;i < N;i++)
        {
            scanf("%s",name);
            int index = HashName(name);
            printf("%s %lu", name, students[index].size());
            sort(students[index].begin(),students[index].end());
            for(int j = 0;j < students[index].size();j++)
            {
                cout << " " << students[index][j];
            }
            cout << endl;
        }
    }
}