ZOJ3068（01分数规划）

本是POJ2976，喜闻乐见的01规划入门题。POJ日常假死，到ZOJ测。

二分答案。

试了试数据好像没问题，\(a_i\)总是小于\(b_i\)且最终预答案l都小于1。然而为什么我把r设成1e10往上就会WA，设成1或者1e3会AC，设成1e2会WA……而且网上题解基本都会被全0的数据hack啊……求解答

#include <cstdio>
#include <cctype>
#include <algorithm>
#define mset(a, b) memset(a, b, sizeof(a))
#define rep(i, a, b) for (int i = a; i <= b; i++)
#define per(i, a, b) for (int i = a; i >= b; i--)
#define fg cout << "--------------\n";
#define debug(x) std::cerr << #x << " = " << x << std::endl
#define All(x) (x.begin()), (x.end())
using namespace std;

typedef double db;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int inf = 0x3f3f3f3f;
const ll INF = 1e18;

template <typename T> void read(T &x) {
	x = 0;
	int s = 1, c = getchar();
	for (; !isdigit(c); c = getchar())
		if (c == '-')	s = -1;
	for (; isdigit(c); c = getchar())
		x = x * 10 + c - 48;
	x *= s;
}

template <typename T> void write(T x) {
	if (x < 0)	x = -x, putchar('-');
	if (x > 9)	write(x / 10);
	putchar(x % 10 + '0');
}

template <typename T> void writeln(T x) {
	write(x);
	puts("");
}

const int maxn = 1e3 + 5;
const db eps = 1e-4;
int n, k;
db a[maxn], b[maxn], c[maxn];

bool not_ok(db mid) {
	db res = 0;
	rep(i, 1, n)	c[i] = a[i] - b[i] * mid, res += c[i];
	sort(c + 1, c + 1 + n);
	rep(i, 1, k)	res -= c[i];
	return res < 0;
}

int main() {
	while (~scanf("%d %d", &n, &k) && (n | k)) {
		db x = 0;
		rep(i, 1, n)	read(a[i]), x += a[i];
		rep(i, 1, n)	read(b[i]);
		if (x == 0.0) {
			puts("0"); continue;
		}
		db l = 0, r = 1;
		while (r - l > eps) {
			db mid = (l + r) / 2.0;
			if (not_ok(mid))	r = mid;
			else	l = mid;
		}
		printf("%.0lf\n", l * 100.0);
	}
	return 0;
}