Codeforces Global Round 2 B. Alyona and a Narrow Fridge(二分)

#include <bits/stdc++.h>
#define maxn 1005
#define ll long long
using namespace std;
ll pre[maxn];
int n;
ll m;

bool cmp(ll a, ll b){
  return a > b;
}

bool Check(ll x){
  vector<ll> v;
  for(int i=0;i<x;i++) v.push_back(pre[i]);
  sort(v.begin(), v.end(), cmp);
  ll ans = m;
  for(int i=0;i<x;i+=2){
    ans -= v[i];
  }
  return ans >= 0;
}

int main()
{
  scanf("%d%lld",&n,&m);
  for(int i=0;i<n;i++){
    scanf("%lld",&pre[i]);
  }
  ll l = 0, r = n, mid, ans = 0;
  while(l <= r){
    mid = (l + r) >> 1;
    if(Check(mid)){
      l = mid + 1;
      ans = mid;
    }
    else r = mid - 1;
  }
  printf("%lld\n", ans);
  return 0;
}