Acwing-3443. 学分绩点

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 20;

int n;
int key[10] = {0, 60, 64, 68, 72, 75, 78, 82, 85, 90}; 
double value[10] = {0, 1.0, 1.5, 2.0, 2.3, 2.7, 3.0, 3.3, 3.7, 4.0};

int grade[N], score[N];

double get(int k)
{
    for (int i = 9; i >= 0; -- i)
        if (k >= key[i]) return value[i];
    return 0;
}

int main()
{
    scanf("%d", &n);
    
    for (int i = 0; i < n; ++ i) scanf("%d", &grade[i]);
    for (int i = 0; i < n; ++ i) scanf("%d", &score[i]);
    
    double sum = 0, cnt = 0;
    for (int i = 0; i < n; ++ i)
    {
        sum += grade[i] * get(score[i]);
        cnt += grade[i];
    }
    
    printf("%.2lf\n", sum / cnt);
    
    return 0;
}