UVA1354MobilingComputing

//UVA1354(2)MobilingComputing#include<cstdio>#include<cstdlib>#include<cstring>#include<vector>using namespace std;struct Tree {double L, R;Tree(): L(0), R(0) {}};//记录结点的左右子树宽度 const int MAXN = 6;double r, w[MAXN], sum[1 << MAXN];//sum用于记录各种情况下的总重，用以计算杆的宽度 vector<Tree> tree[1 << MAXN];//用来保存每一种根树下每一颗合法子树的左右最大宽度 int vis[1 << MAXN];//判重 int s;void dfs(int subset) {if(vis[subset]) return;vis[subset] = true;bool have_spring = false;for(int left = (subset - 1) & subset; left; left = (left - 1) & subset) {have_spring = true;//当left非零时，说明有后代 int right = left ^ subset;//在父代基础上，左子树的异或结果是相应的右子树 double d1 = sum[right] / sum[subset];//左侧杆长 double d2 = sum[left] / sum[subset];//右侧杆长 dfs(left); dfs(right);for(int i = 0; i < tree[left].size(); i++) {for(int j = 0; j < tree[right].size(); j++) {Tree t;t.L = max(tree[left][i].L + d1, tree[right][j].L - d2);t.R = max(tree[left][i].R - d1, tree[right][j].R + d2);if(t.R + t.L < r) tree[subset].push_back(t);}}}if(!have_spring) tree[subset].push_back(Tree());//适用于叶结点，左右宽度均为0 }int main() {int T;scanf("%d", &T);while(T--) {memset(vis, 0, sizeof(vis));scanf("%lf%d", &r, &s);for(int i = 0; i < s; i++) scanf("%lf", &w[i]);for(int i = 0; i < (1 << s); i++) {sum[i] = 0;tree[i].clear();//初始化 for(int j = 0; j < s; j++) {if(i & (1 << j)) sum[i] += w[j];//计算每一种分配下的总重 }}int root = (1 << s) - 1;dfs(root);//root的值表示其带有所有的重物（因为其二进制表示每一位均为1） double ans = -1;for(int i = 0; i < tree[root].size(); i++){ans = max(ans, tree[root][i].L + tree[root][i].R);}printf("%.16lf\n", ans);}return 0;} /*51.33  1211.431212.031211.59421131.714341235*/