結果

問題 No.2012 Largest Triangle
ユーザー tnakao0123
提出日時 2024-07-23 17:54:00
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
WA  
実行時間 -
コード長 1,580 bytes
コンパイル時間 733 ms
コンパイル使用メモリ 62,896 KB
最終ジャッジ日時 2025-02-23 17:54:16
ジャッジサーバーID
(参考情報)
judge1 / judge1
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ファイルパターン 結果
sample AC * 1
other AC * 17 WA * 24
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.cpp: In function ‘int main()’:
main.cpp:38:8: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   38 |   scanf("%d", &n);
      |   ~~~~~^~~~~~~~~~
main.cpp:39:36: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   39 |   for (int i = 0; i < n; i++) scanf("%lld%lld", xs + i, ys + i);
      |                               ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

ソースコード

diff #

/* -*- coding: utf-8 -*-
 *
 * 2012.cc:  No.2012 Largest Triangle - yukicoder
 */

#include<cstdio>
#include<cmath>
#include<algorithm>
#include<utility>

using namespace std;

/* constant */

const int MAX_N = 200000;
const long long LINF = 1LL << 60;

/* typedef */

using ll = long long;
using pdi = pair<double,int>;

/* global variables */

ll xs[MAX_N], ys[MAX_N];
pdi tis[MAX_N];

/* subroutines */

inline ll cross(int i, int j) {
  return xs[i] * ys[j] - xs[j] * ys[i];
}

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%lld%lld", xs + i, ys + i);

  for (int i = 0; i < n; i++) tis[i] = {atan2(ys[i], xs[i]), i};
  sort(tis, tis + n);

  ll minc = LINF, maxc = -LINF;
  int j0 = -1, j1 = -1;
  for (int j = 0; j < n; j++) {
    ll c = cross(0, tis[j].second);
    //printf(" c=%lld,j=%d\n", c, j);
    if (minc > c) minc = c, j0 = j;
    if (maxc < c) maxc = c, j1 = j;
  }
  //printf("minc=%lld,j0=%d maxc=%lld,j1=%d\n", minc, j0, maxc, j1);

  for (int i = 1; i < n; i++) {
    ll c0 = cross(tis[i].second, tis[j0].second);
    while (j0 != i) {
      int jj = (j0 + 1) % n;
      ll cc = cross(tis[i].second, tis[jj].second);
      if (cc >= c0) break;
      c0 = cc, j0 = jj;
    }
    minc = min(minc, c0);

    ll c1 = cross(tis[i].second, tis[j1].second);
    while (j1 != i) {
      int jj = (j1 + 1) % n;
      ll cc = cross(tis[i].second, tis[jj].second);
      if (cc <= c1) break;
      c1 = cc, j1 = jj;
    }
    maxc = max(maxc, c1);
  }

  ll maxs = max(-minc, maxc);
  printf("%lld\n", maxs);
  
  return 0;
}
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