【DP】uva1354

因为代码不是自己写的所以就算转载吧。

大体思想是想出来的，就是二进制枚举，但是实现实在有点写不来。。。

#include<iostream>
#include<algorithm>
#include<string>
#include<sstream>
#include<set>
#include<vector>
#include<stack>
#include<map>
#include<queue>
#include<cassert>
#include<cstdlib>
#include<cstdio>
#include<ctime>
#include<cmath>
#include<cstring>
#include<functional>
using namespace std;
#define INF 0x3f3f3f3f
#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)<(b)?(a):(b))
using namespace std;
const int N = 6;
const int MAXN = (1 << N);
int t, n, i, j, vis[MAXN];
double w[N], sumw[MAXN], r;
struct Node {
	double l, r;
	Node() {}
	Node(double ll, double rr) { l = ll; r = rr; }
};
vector<Node> node[MAXN];

int bitcount(int x) {  
	if (x == 0) return 0;
	return bitcount(x / 2) + (x & 1);
}

void dfs(int s) {
	if (vis[s]) return;
	vis[s] = 1;
	if (bitcount(s) == 1) {  
		node[s].push_back(Node(0, 0));
		return;
	}
	for (int l = (s - 1)&s; l > 0; l = (l - 1)&s) { 
		int r = s^l;
		dfs(l); dfs(r);
		for (int i = 0; i < node[l].size(); i++) {
			for (int j = 0; j < node[r].size(); j++) {
				double ll = min(-sumw[r] / (sumw[l] + sumw[r]) + node[l][i].l, sumw[l] / (sumw[l] + sumw[r]) + node[r][j].l);
				double rr = max(sumw[l] / (sumw[l] + sumw[r]) + node[r][j].r, -sumw[r] / (sumw[l] + sumw[r]) + node[l][i].r);
				node[s].push_back(Node(ll, rr));
			}
		}
	}
}

void solve() {
	double ans = -1;
	int s = (1 << n) - 1;
	dfs(s);
	for (int i = 0; i < node[s].size(); i++) {
		if (node[s][i].r - node[s][i].l < r) {
			if (node[s][i].r - node[s][i].l > ans)
				ans = node[s][i].r - node[s][i].l;
		}
	}
	if (ans == -1) printf("-1\n");
	else printf("%.10lf\n", ans);
}

int main() {
	scanf("%d", &t);
	while (t--) {
		memset(vis, 0, sizeof(vis));
		memset(node, 0, sizeof(node));
		scanf("%lf%d", &r, &n);
		for (i = 0; i < n; i++)
			scanf("%lf", &w[i]);
		for (i = 0; i < (1 << n); i++) {
			sumw[i] = 0;
			for (j = 0; j < n; j++) {
				if (i&(1 << j))
					sumw[i] += w[j];
			}
		}
		solve();
	}
	return 0;
}