01背包分支限界算法C++

以下是01背包分支限界算法的C++代码实现：

#include <iostream>
#include <algorithm>
#include <queue>

using namespace std;

const int N = 1010;

struct Node
{
    int v, w;
    double u; // u表示单位价值
    bool operator< (const Node &t) const
    {
        return u < t.u;
    }
}node[N];

int n, m;
double ans;
priority_queue<double> q;

void dfs(int u, int v, double w)
{
    if (v > m) return;
    if (u == n)
    {
        ans = max(ans, w);
        return;
    }
    if (w + q.top() * (m - v + 1) <= ans) return; // 剪枝
    q.push(node[u + 1].u);
    dfs(u + 1, v + node[u + 1].v, w + node[u + 1].w);
    q.pop();
    dfs(u + 1, v, w);
}

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i ++ )
    {
        cin >> node[i].v >> node[i].w;
        node[i].u = (double)node[i].w / node[i].v;
    }
    sort(node + 1, node + n + 1);
    dfs(0, 0, 0);
    printf("%.2lf\n", ans);
    return 0;
}