Problem p03465 (C++)

Buggy submission (status: Time Limit Exceeded):
#include "bits/stdc++.h"
// #include "ext/pb_ds/tree_policy.hpp"
// #include "ext/pb_ds/assoc_container.hpp"
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (int x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(a.begin(), a.end()), a.end())
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) a.begin(), a.end()
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define sqr(x) ((x) * (x))
#define lowbit(x) (x & (-x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define dbg(x) cerr << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;
const int block_size = 320;
typedef complex<ll> point;
const ll mod = 1e9 + 7;
const ll inf = 1e9 + 7;
const ld eps = 1e-9;
const db PI = atan(1) * 4;
template <typename T> inline int sign(const T &a) {
  if (a < 0)
    return -1;
  if (a > 0)
    return 1;
  return 0;
}

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

template <typename T> inline void in(T &x) {
  x = 0;
  T f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-')
      f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  x *= f;
}

ll twop(int x) { return 1LL << x; }

template <typename A, typename B> inline void in(A &x, B &y) {
  in(x);
  in(y);
}
template <typename A, typename B, typename C> inline void in(A &x, B &y, C &z) {
  in(x);
  in(y);
  in(z);
}
template <typename A, typename B, typename C, typename D>
inline void in(A &x, B &y, C &z, D &d) {
  in(x);
  in(y);
  in(z);
  in(d);
}

bitset<4000001> b;
int main() {
#ifndef ONLINE_JUDGE
  fr("/Users/zhangqingchuan/Desktop/cp/cp/input.txt");
  fw("/Users/zhangqingchuan/Desktop/cp/cp/output.txt");
#endif
  b[0] = 1;
  int n;
  in(n);
  int sum = 0;
  REP(i, 0, n) {
    int c;
    in(c);
    b |= b << c;
    sum += c;
  }

  REP(i, (sum + 1) / 2, sum + 1) {
    if (b[i]) {
      return printf("%d", i), 0;
    }
  }

  return 0;
}


Fixed submission:
#include "bits/stdc++.h"
// #include "ext/pb_ds/tree_policy.hpp"
// #include "ext/pb_ds/assoc_container.hpp"
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (int x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(a.begin(), a.end()), a.end())
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) a.begin(), a.end()
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define sqr(x) ((x) * (x))
#define lowbit(x) (x & (-x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define dbg(x) cerr << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;
const int block_size = 320;
typedef complex<ll> point;
const ll mod = 1e9 + 7;
const ll inf = 1e9 + 7;
const ld eps = 1e-9;
const db PI = atan(1) * 4;
template <typename T> inline int sign(const T &a) {
  if (a < 0)
    return -1;
  if (a > 0)
    return 1;
  return 0;
}

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

template <typename T> inline void in(T &x) {
  x = 0;
  T f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-')
      f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  x *= f;
}

ll twop(int x) { return 1LL << x; }

template <typename A, typename B> inline void in(A &x, B &y) {
  in(x);
  in(y);
}
template <typename A, typename B, typename C> inline void in(A &x, B &y, C &z) {
  in(x);
  in(y);
  in(z);
}
template <typename A, typename B, typename C, typename D>
inline void in(A &x, B &y, C &z, D &d) {
  in(x);
  in(y);
  in(z);
  in(d);
}

bitset<4000001> b;
int main() {
  b[0] = 1;
  int n;
  in(n);
  int sum = 0;
  REP(i, 0, n) {
    int c;
    in(c);
    b |= b << c;
    sum += c;
  }

  REP(i, (sum + 1) / 2, sum + 1) {
    if (b[i]) {
      return printf("%d", i), 0;
    }
  }

  return 0;
}