POJ2976 题解 0/1分数规划入门题 二分

题目链接：http://poj.org/problem?id=2976

关于 0/1分数规划 参见 这篇博客

实现代码如下：

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;
const int maxn = 1010;
const double eps = 1e-4;
int n, k;
double a[maxn], b[maxn], c[maxn];
inline bool cmp(double a, double b) { return a > b; }
bool check(double x) {
    for (int i = 0; i < n; i ++) c[i] = a[i] - x * b[i];
    sort(c, c+n, cmp);
    double tmp = 0;
    for (int i = 0; i < n-k; i ++) tmp += c[i];
    return tmp >= 0;
}
void solve() {
    double L = 0, R = 1, res;
    while (R - L > eps) {
        double mid = (L + R) / 2.0;
        if (check(mid)) {
            res = mid;
            L = mid;
        }
        else
            R = mid;
    }
    printf("%.0f\n", res * 100);
}
int main() {
    while ( ~scanf("%d%d", &n, &k) && n ) {
        for (int i = 0; i < n; i ++) scanf("%lf", a+i);
        for (int i = 0; i < n; i ++) scanf("%lf", b+i);
        solve();
    }
    return 0;
}