51nod 1351 吃点心（贪心）

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn = 50+5;

int n,c,x,lowtot,hightot;

struct node
{
int low,high;
bool operator< (const node& rhs) const
{
return low > rhs.low;
}
}a[maxn];

bool cmp(node a, node b)
{
return a.high>b.high;
}

int main()
{
//freopen("in.txt","r",stdin);
int T;
scanf("%d",&T);
while(T--)
{
lowtot = hightot = 0;
scanf("%d%d%d",&n,&c,&x);
for(int i=1;i<=n;i++)
{
scanf("%d%d",&a[i].low,&a[i].high);
lowtot += a[i].low;
hightot += a[i].high;
}
int sum = 0;
int ans = 0;
sort(a+1,a+n+1);
int tmp = hightot;
for(int i=1;i<=n;i++)
{
sum += a[i].low;
ans++;
hightot -= a[i].high;
if(sum>=x || c-hightot>=x)  break;
}

sum = 0;
int ans2 = 0;
sort(a+1,a+n+1,cmp);
hightot = tmp;
for(int i=1;i<=n;i++)
{
sum += a[i].low;
ans2++;
hightot -= a[i].high;
if(sum>=x || c-hightot>=x)  break;
}
printf("%d\n",min(ans,ans2));
}
return 0;
}