01分数规划

OI分数规划

首先，单纯的贪心是错误的(废话)

除了常见的二分之外还有一种调整法，不会.....

板题：POJ2976 Dropping tests

#include <cstdio>
#include <algorithm>

typedef long long LL;
const int N = 1010;
const double INF = 1e11;

struct Node {
    double a, b, c;
    inline bool operator <(const Node &w) const {
        return c < w.c;
    }
}node[N];

int n, k;

inline bool check(double D) {
    for(int i = 1; i <= n; i++) {
        node[i].c = node[i].a - node[i].b * D;
    }
    std::sort(node + 1, node + n + 1);
    //printf("k = %d 
", k);
    double ans = 0;
    for(int i = 1; i <= k; i++) {
        ans += node[n + 1 - i].c;
    }
    return ans >= 0;
}

inline void solve() {
    k = n - k;
    double l = INF, r = -INF;
    for(int i = 1; i <= n; i++) {
        scanf("%lf", &node[i].a);
    }
    for(int i = 1; i <= n; i++) {
        scanf("%lf", &node[i].b);
        double temp = node[i].a / node[i].b;
        l = std::min(l, temp);
        r = std::max(r, temp);
    }

    for(int i = 1; i <= 50; i++) {
        double mid = (l + r) / 2;
        if(check(mid)) {
            l = mid;
        }
        else {
            r = mid;
        }
    }
    printf("%lld
", (LL)(r * 100 + 0.5));
    return;
}

int main() {
    while(scanf("%d%d", &n, &k)) {
        if(!n && !k) break;
        solve();
    }

    return 0;
}