优化过程的一道题

约定不等于承诺〃 2023-09-23 22:31 112阅读 0赞

[3443. 学分绩点 - AcWing题库][3443. _ - AcWing]

**来源：北京大学考研机试题**

![2c4267a416ea435c8b9468f358ead6c6.png][]

**优化前**

#include <iostream>
    #include <cstring>
    #include <algorithm>
    
    using namespace std;
    const int N = 100010;
    int a[N],b[N];
    
    double jidian(int x) { 
        if(x >= 90 && x <= 100) return 4.0;
        else if(x >= 85 && x <= 89) return 3.7;
        else if(x >= 82 && x <= 84) return 3.3;
        else if(x >= 78 && x <= 81) return 3.0;
        else if(x >= 75 && x <= 77) return 2.7;
        else if(x >= 72 && x <= 74) return 2.3;
        else if(x >= 68 && x <= 71) return 2.0;
        else if(x >= 64 && x <= 67) return 1.5;
        else if(x >= 60 && x <= 63) return 1.0;
        else return 0;
    }
    
    int main()
    {
        int n;
        double sum=0.0,cnt=0;
        scanf("%d\n", &n);
        for (int i = 0; i < n; i ++ )
        {
            scanf("%d", &a[i]);
            cnt+=a[i];
        }
        for (int i = 0; i < n; i ++ )
        {
            scanf("%d", &b[i]);
        }
        for (int i = 0; i < n; i ++ )
        {
            sum+=jidian(b[i])*a[i];
        }
        printf("%.2f",sum/cnt);
    }

**优化后**

#include <iostream>
    #include <cstring>
    #include <algorithm>
    
    using namespace std;
    
    const int N = 20;
    
    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 a[N], b[N];
    
    double jidian(int x)
    {
        for (int i = 9; i >= 0; i -- )
            if (x >= key[i])
                return value[i];
        return 0;
    }
    
    int main()
    {
        int n;
        cin >> n;
    
        for (int i = 0; i < n; i ++ ) cin >> a[i];
        for (int i = 0; i < n; i ++ ) cin >> b[i];
    
        double sum = 0, cnt = 0;
        for (int i = 0; i < n; i ++ )
        {
            sum += jidian(b[i]) * a[i];
            cnt += a[i];
        }
    
        printf("%.2lf\n", sum / cnt);
        return 0;
    }

[3443. _ - AcWing]: https://www.acwing.com/problem/content/description/3446/
[2c4267a416ea435c8b9468f358ead6c6.png]: https://img-blog.csdnimg.cn/2c4267a416ea435c8b9468f358ead6c6.png