POJ - 3111 K Best 平均值最大（01分数规划）

[code]#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
#define maxn 100010
int n, k, ans[maxn];
double Sum;
struct jewels {
    double v, w, d;
    int id;
}J[maxn];

bool cmp(const jewels a, const jewels b) {
    return a.d > b.d;
}

bool judge(double mid) {

    for(int i = 0; i < n; i++)
        J[i].d = J[i].v - mid * J[i].w;
    sort(J, J + n, cmp);
    double t = 0.0;
    for(int i = 0; i < k; i++)
        t += J[i].d;
    return t >= 0;
}

void solve() {
    double l = 0, r = 1e7 + 1;
    while(r - l > 1e-6) {
        double mid = (l + r) / 2;
        if(judge(mid))
            l = mid;
        else
            r = mid;
    }
}

int main() {
    while(scanf("%d%d", &n, &k) != EOF) {
        for(int i = 0; i < n; i++) {
            scanf("%lf%lf", &J[i].v, &J[i].w);
            J[i].id = i + 1;
        }
        solve();
        printf("%d", J[0].id);
        for(int i = 1; i < k; i++)
            printf(" %d", J[i].id);
        printf("\n");
    }
    return 0;
}