题解 | #奖学金#

using System;
public class Program {
    public static void Main() {
        string line;
        while ((line = Console.ReadLine()) != null) {
            //录入第一行
            string[] strings = line.Split(' ');
            int[] nra = new int[strings.Length];
            for (int i = 0; i < nra.Length; i++) {
                nra[i] = int.Parse(strings[i]) ;
            }
            int[] grade = new int [nra[0]];
            int[] time = new int [nra[0]];
            int maxgrade = nra[1];
            int targetavg = nra[2];
            long usetime = 0;
            //录入分数和复习用时
            for (int i = 0; i < nra[0]; i++) {
                line = Console.ReadLine();
                strings = line.Split(' ');
                grade[i] = int.Parse(strings[0]);
                time[i] = int.Parse(strings[1]);
            }
            float avg = 0;
            float sum = 0;
            foreach(int i in grade){
                sum += i;
            }
            avg = sum / nra[0];
            //贪心算时间
            while((int)avg < targetavg){
                int mintime = -1;
                int index = 0;
                for(int i = 0; i < nra[0]; i++){
                    if(grade[i] == maxgrade) continue;
                    if(mintime == -1 || time[i] < mintime){
                        index = i;
                        mintime = time[i];
                    }
                }
                grade[index]++;
                sum++;
                avg = sum / nra[0];
                usetime += mintime;
            }
            Console.WriteLine(usetime);
        }
    }
}

思路：每次从分数未满的课中选择需要最少复习时间的课进行复习，复习之后总分++，用时+=复习用时，课程分数++

这里有个坑，用时需要用long型，否则有个案例不通过