Problem p02321 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
int const MOD = 1000000007;
ll mod_pow(ll x, ll n) {
  return (!n) ? 1 : (mod_pow((x * x) % MOD, n / 2) * ((n & 1) ? x : 1)) % MOD;
}
int madd(int a, int b) { return (a + b) % MOD; }
int msub(int a, int b) { return (a - b + MOD) % MOD; }
int mmul(int a, int b) { return (a * b) % MOD; }
int minv(int a) { return mod_pow(a, MOD - 2); }
int mdiv(int a, int b) { return mmul(a, minv(b)); }

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

int N, W;
int v[50], w[50];

vector<pii> generate(int s, int n) {
  vector<pii> ret;
  rep(bit, 0, 1 << n) {
    int value = 0, weight = 0;
    rep(i, 0, n) {
      if (bit >> i & 1) {
        value += v[s + i];
        weight += w[s + i];
      }
    }
    if (weight <= W)
      ret.pb(pii(weight, value));
  }
  sort(ret.begin(), ret.end());
  return ret;
}

void solve() {
  int r1 = N / 2, r2 = N - r1;
  vector<pii> tb1 = generate(0, r1), tb2 = generate(r1, r2);

  int ans = 0, t = 0, ma = 0;
  repr(i, tb1.size() - 1, 0) {
    int nw = tb1[i].fr, nc = tb1[i].sc;
    while (t < tb2.size() && tb2[t].fr + nw <= W) {
      ma = max(ma, tb2[t++].sc);
    }
    ans = max(ans, ma + nc);
  }
  cout << ans << endl;
}

signed main() {
  cin >> N >> W;
  rep(i, 0, N) cin >> v[i] >> w[i];
  solve();
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
int const MOD = 1000000007;
ll mod_pow(ll x, ll n) {
  return (!n) ? 1 : (mod_pow((x * x) % MOD, n / 2) * ((n & 1) ? x : 1)) % MOD;
}
int madd(int a, int b) { return (a + b) % MOD; }
int msub(int a, int b) { return (a - b + MOD) % MOD; }
int mmul(int a, int b) { return (a * b) % MOD; }
int minv(int a) { return mod_pow(a, MOD - 2); }
int mdiv(int a, int b) { return mmul(a, minv(b)); }

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

int N, W;
int v[50], w[50];

vector<pii> generate(int s, int n) {
  vector<pii> ret;
  rep(bit, 0, 1 << n) {
    int value = 0, weight = 0;
    rep(i, 0, n) {
      if (bit >> i & 1) {
        value += v[s + i];
        weight += w[s + i];
      }
    }
    if (weight <= W)
      ret.pb(pii(weight, value));
  }
  sort(ret.begin(), ret.end());
  return ret;
}

void solve() {
  int r1 = N / 2, r2 = N - r1;
  vector<pii> tb1 = generate(0, r1), tb2 = generate(r1, r2);

  int ans = 0;
  repr(i, tb1.size() - 1, 0) {
    int t = 0, nw = tb1[i].fr, nc = tb1[i].sc;
    while (t < tb2.size() && tb2[t].fr + nw <= W) {
      ans = max(ans, nc + tb2[t++].sc);
    }
  }
  cout << ans << endl;
}

signed main() {
  cin >> N >> W;
  rep(i, 0, N) cin >> v[i] >> w[i];
  solve();
  return 0;
}