題目大意：
n個物體 每個物品有體積和價值，取V體積問最大價值。

揹包，不過資料很大……
然後……先寫個暴力的dfs，TLE
然後按價效比排個序，TLE
然後加各種剪枝，TLE

賽後(clock()-st)/CLOCKS_PER_SEC <= 0.02 st為dfs前取的clock()
跑的比誰都快……不想說話。。

程式碼如下：

#include <iostream>
#include <cmath>
#include <vector>
#include <cstdlib>
#include <cstdio>
#include <climits>
 

#include <ctime>
#include <cstring>
#include <queue>
#include <stack>
#include <list>
#include <algorithm>
#include <map>
#include <set>
#define LL long long
#define Pr pair<int,int>
#define fread(ch) freopen(ch,"r",stdin)
#define fwrite(ch) freopen(ch,"w",stdout)
 


using namespace std;
const int INF = 0x3f3f3f3f;
const int msz = 10000;
const int mod = 1e9+7;
const double eps = 1e-8;

struct Obj
{
    LL v,w;
    double xjb;
    bool operator < (const struct Obj a)const
    {
        return xjb > a.xjb;
    }
} obj[111];

int n;
LL v,mn;
LL ans;
double c;

void
 
 dfs(int pos,LL sum,LL v)
{
    if((clock()-c)/CLOCKS_PER_SEC > 0.02) return;
    ans = max(ans,sum);
    if(sum+obj[pos].xjb*v < ans) return;
    if(v < mn) return;
    if(pos == n) return;

    if(obj[pos].v <= v) dfs(pos+1,sum+obj[pos].w,v-obj[pos].v);
    dfs(pos+1,sum,v);
}

int main()
{
    //fread("");
    //fwrite("");

    while(~scanf("%d%lld",&n,&v))
    {
        mn = 1e9+7;
        for(int i = 0; i < n; ++i)
        {
            scanf("%lld%lld",&obj[i].v,&obj[i].w);
            obj[i].xjb = obj[i].w*1.0/obj[i].v;
            mn = min(mn,obj[i].v);
        }

        sort(obj,obj+n);

        ans = 0;
        c = clock();
        dfs(0,0,v);

        printf("%lld\n",ans);
    }

    return 0;
}