洛谷PP1570 KC 喝咖啡

本题做法

• 01分数规划+二分答案。

思路

二分答案\(x\)，\(check\)函数内部将每个调料的\(v_i-xc_i\)求出，再从大到小排序，将前\(m\)个的值累加，返回这个和是否大于等于0。

代码

#include <bits/stdc++.h>
#define endl '\n'
#define ll long long

using namespace std;

const int INF = 0x3f3f3f3f;
const double EPS = 1e-8;
const int N = 205;

int n, m;
double v[N], c[N], h[N];

bool check(double x) {
    for (int i = 1; i <= n; i++)
        h[i] = v[i] - x * c[i];
    sort(h + 1, h + 1 + n, greater<double>());
    double s = 0;
    for (int i = 1; i <= m; i++)
        s += h[i];
    return s >= 0;
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        cin >> v[i];
    for (int i = 1; i <= n; i++)
        cin >> c[i];
    double l = 0, r = 1001;
    while (r - l > EPS) {
        double mid = (l + r) / 2;
        if (check(mid))
            l = mid;
        else
            r = mid;
    }
    printf("%.3lf\n", l);
    return 0;
}