AtCoder Regular Contest 031

ARC

C++

22 Dec 2014

AtCoder Regular Contest 031

C. 積み木

愚直アプローチ

ナイーブに反転数を求める.

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <utility>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <cstdio>

using namespace std;

#define REP(i,n) for((i)=0;(i)<(int)(n);(i)++)
#define foreach(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)

ll solve() {
  vector<P> vp;
  for (int i = 0; i < n; i++) {
    vp.push_back(P(b[i], i));
  }

  sort(vp.begin(), vp.end());

  ll ans = 0;

  for(int i = 0; i < n; i++) {
    P p = vp[i];
    int idx = p.second;
    int val = p.first;

    // l
    ll lcnt = 0;
    for (int j = idx - 1; j >= 0; j--) {
      if (b[j] == -1) continue;
      //printf("lcnt - %d vs %d\n", val, b[j]);
      if (val < b[j]) {
        ++lcnt;
      }
    }

    // r
    ll rcnt = 0;
    for (int j = idx + 1; j < n; j++) {
      if (b[j] == -1) continue;
      //printf("rcnt - %d vs %d\n", val, b[j]);
      if (val < b[j]) ++rcnt;
    }
    ans += min(lcnt, rcnt);
    b[idx] = -1;
  }
  return ans;
}

int main() {
  while (cin >> n) {
    for(size_t i = 0; i < n; i++)
    {
      cin >> b[i];
    }
    printf("%lld\n", solve());
  }
  return 0;
}

BIT(Binary Indexed Tree)

小さい方 or 大きい方から順番に対応する場所に add していって, 左側と右側の場合の反転数を Bit で lgN で計算する.

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <utility>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <cstdio>

using namespace std;

#define REP(i,n) for((i)=0;(i)<(int)(n);(i)++)
#define foreach(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)

int b[100020], n;

struct Bit {
  const int N;
  vector<int> data;
  Bit(const int size) : N(size + 2), data(n + 4) {}
  void add(int idx, int value) {
    for (int x = idx; x <= N; x += x & -x)
      data[x] += value;
  }
  int sum(int idx) {
    int ret = 0;
    for (int x = idx; x > 0; x -= x & -x)
      ret += data[x];
    return ret;
  }
};

typedef long long ll;

typedef pair<int,int> P;

ll solve() {
  ll ans = 0;
  Bit bit(n);

  vector<P> vp;
  for(int i = 0; i < n; i++)
  {
    vp.push_back(P(b[i], i+1));
  }

  sort(vp.begin(), vp.end(), greater<P>());

  for(int i = 0; i < n; i++)
  {
    int idx = vp[i].second;
    int lhs = bit.sum(idx);
    int rhs = bit.sum(n) - lhs;
    ans += min(lhs, rhs);
    bit.add(idx, 1);
  }
  return ans;
}

int main() {
  while (cin >> n) {
    for(size_t i = 0; i < n; i++)
    {
      cin >> b[i];
    }
    printf("%lld\n", solve());
  }
  return 0;
}

D. 買い物上手

全探索アプローチ

全探索をナイーブに実装すれば部分点は取れる.

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <utility>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <cstdio>

using namespace std;

#define REP(i,n) for((i)=0;(i)<(int)(n);(i)++)
#define foreach(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)

int N, M;

int S[102], T[102], K[102];

int A[102][102];

double solve() {
  double ans = 0;
  for (int Set = 0; Set < (1<<N); Set++) {
    bitset<102> bs;
    int exp = 0;
    for (int i = 0; i < N; i++) {
      if (!(Set >> i & 1)) continue;
      exp += S[i];
      for (int j = 0; j < K[i]; j++) {
        bs.set(A[i][j]);
      }
    }
    int sum = 0;
    for (int i = 0; i < M; i++) {
      if (bs[i]) sum += T[i];
    }
    ans = max(ans, (double)exp / sum);
  }
  return ans;
}

int main() {
  while (cin >> N >> M) {
    for(size_t i = 0; i < N; i++)
    {
      cin>>S[i];
    }
    for(size_t i = 0; i < M; i++)
    {
      cin>>T[i];
    }
    for(size_t i = 0; i < N; i++)
    {
      cin>>K[i];
      for(size_t j = 0; j < K[i]; j++)
      {
        cin>>A[i][j];
        A[i][j]--;
      }
    }
    printf("%lf\n", solve());
  }

  return 0;
}

最大流

解説解読中….